feat(types): Add GitLab Resource Event serde types with deserialization tests

Adds six new types for deserializing responses from GitLab's three
Resource Events API endpoints (state, label, milestone):

- GitLabStateEvent: State transitions with optional user, source_commit,
  and source_merge_request reference
- GitLabLabelEvent: Label add/remove events with nested GitLabLabelRef
- GitLabMilestoneEvent: Milestone assignment changes with nested
  GitLabMilestoneRef
- GitLabMergeRequestRef: Lightweight MR reference (iid, title, web_url)
- GitLabLabelRef: Label metadata (id, name, color, description)
- GitLabMilestoneRef: Milestone metadata (id, iid, title)

All types derive Deserialize + Serialize and use Option<T> for nullable
fields (user, source_commit, color, description) to match GitLab's API
contract where these fields may be null.

Includes 8 new test cases covering:
- State events with/without user, with/without source_merge_request
- Label events for add and remove actions, including null color handling
- Milestone event deserialization
- Standalone ref type deserialization (MR, label, milestone)

Uses r##"..."## raw string delimiters where JSON contains hex color
codes (#FF0000) that would conflict with r#"..."# delimiters.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/gitlab/mod.rs

@@ -10,6 +10,7 @@ pub use transformers::{
     transform_discussion, transform_issue, transform_notes,
 };
 pub use types::{
-    GitLabAuthor, GitLabDiscussion, GitLabIssue, GitLabNote, GitLabNotePosition, GitLabProject,
-    GitLabUser, GitLabVersion,
+    GitLabAuthor, GitLabDiscussion, GitLabIssue, GitLabLabelEvent, GitLabLabelRef,
+    GitLabMergeRequestRef, GitLabMilestoneEvent, GitLabMilestoneRef, GitLabNote,
+    GitLabNotePosition, GitLabProject, GitLabStateEvent, GitLabUser, GitLabVersion,
 };

src/gitlab/types.rs

@@ -182,6 +182,70 @@ impl GitLabLineRange {
     }
 }
 
+// === Resource Event types (Phase B - Gate 1) ===
+
+/// Reference to an MR in state event's source_merge_request field.
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct GitLabMergeRequestRef {
+    pub iid: i64,
+    pub title: Option<String>,
+    pub web_url: Option<String>,
+}
+
+/// Reference to a label in label event's label field.
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct GitLabLabelRef {
+    pub id: i64,
+    pub name: String,
+    pub color: Option<String>,
+    pub description: Option<String>,
+}
+
+/// Reference to a milestone in milestone event's milestone field.
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct GitLabMilestoneRef {
+    pub id: i64,
+    pub iid: i64,
+    pub title: String,
+}
+
+/// State change event from the Resource State Events API.
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct GitLabStateEvent {
+    pub id: i64,
+    pub user: Option<GitLabAuthor>,
+    pub created_at: String,
+    pub resource_type: String,
+    pub resource_id: i64,
+    pub state: String,
+    pub source_commit: Option<String>,
+    pub source_merge_request: Option<GitLabMergeRequestRef>,
+}
+
+/// Label change event from the Resource Label Events API.
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct GitLabLabelEvent {
+    pub id: i64,
+    pub user: Option<GitLabAuthor>,
+    pub created_at: String,
+    pub resource_type: String,
+    pub resource_id: i64,
+    pub label: GitLabLabelRef,
+    pub action: String,
+}
+
+/// Milestone change event from the Resource Milestone Events API.
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct GitLabMilestoneEvent {
+    pub id: i64,
+    pub user: Option<GitLabAuthor>,
+    pub created_at: String,
+    pub resource_type: String,
+    pub resource_id: i64,
+    pub milestone: GitLabMilestoneRef,
+    pub action: String,
+}
+
 // === Checkpoint 2: Merge Request types ===
 
 /// GitLab MR references (short and full reference strings).

tests/gitlab_types_tests.rs

@@ -1,8 +1,10 @@
 //! Tests for GitLab API response type deserialization.
 
 use lore::gitlab::types::{
-    GitLabAuthor, GitLabDiscussion, GitLabIssue, GitLabMergeRequest, GitLabMilestone, GitLabNote,
-    GitLabNotePosition, GitLabReferences, GitLabReviewer,
+    GitLabAuthor, GitLabDiscussion, GitLabIssue, GitLabLabelEvent, GitLabLabelRef,
+    GitLabMergeRequest, GitLabMergeRequestRef, GitLabMilestone, GitLabMilestoneEvent,
+    GitLabMilestoneRef, GitLabNote, GitLabNotePosition, GitLabReferences, GitLabReviewer,
+    GitLabStateEvent,
 };
 
 #[test]
@@ -637,3 +639,209 @@ fn deserializes_diffnote_position_with_line_range() {
     assert_eq!(range.start_line(), Some(10));
     assert_eq!(range.end_line(), Some(15));
 }
+
+// === Resource Event type tests ===
+
+#[test]
+fn deserializes_state_event_closed_by_mr() {
+    let json = r#"{
+        "id": 1001,
+        "user": {
+            "id": 42,
+            "username": "developer",
+            "name": "Dev User"
+        },
+        "created_at": "2024-03-15T10:30:00.000Z",
+        "resource_type": "Issue",
+        "resource_id": 555,
+        "state": "closed",
+        "source_commit": null,
+        "source_merge_request": {
+            "iid": 99,
+            "title": "Fix the bug",
+            "web_url": "https://gitlab.example.com/group/project/-/merge_requests/99"
+        }
+    }"#;
+
+    let event: GitLabStateEvent =
+        serde_json::from_str(json).expect("Failed to deserialize state event");
+
+    assert_eq!(event.id, 1001);
+    assert!(event.user.is_some());
+    assert_eq!(event.user.as_ref().unwrap().username, "developer");
+    assert_eq!(event.resource_type, "Issue");
+    assert_eq!(event.resource_id, 555);
+    assert_eq!(event.state, "closed");
+    assert!(event.source_commit.is_none());
+    assert!(event.source_merge_request.is_some());
+    let mr_ref = event.source_merge_request.unwrap();
+    assert_eq!(mr_ref.iid, 99);
+    assert_eq!(mr_ref.title, Some("Fix the bug".to_string()));
+}
+
+#[test]
+fn deserializes_state_event_simple_no_user() {
+    let json = r#"{
+        "id": 1002,
+        "user": null,
+        "created_at": "2024-03-15T10:30:00.000Z",
+        "resource_type": "MergeRequest",
+        "resource_id": 777,
+        "state": "merged",
+        "source_commit": "abc123def456",
+        "source_merge_request": null
+    }"#;
+
+    let event: GitLabStateEvent =
+        serde_json::from_str(json).expect("Failed to deserialize state event without user");
+
+    assert_eq!(event.id, 1002);
+    assert!(event.user.is_none());
+    assert_eq!(event.resource_type, "MergeRequest");
+    assert_eq!(event.state, "merged");
+    assert_eq!(event.source_commit, Some("abc123def456".to_string()));
+    assert!(event.source_merge_request.is_none());
+}
+
+#[test]
+fn deserializes_label_event_add() {
+    let json = r##"{
+        "id": 2001,
+        "user": {
+            "id": 42,
+            "username": "developer",
+            "name": "Dev User"
+        },
+        "created_at": "2024-03-15T10:30:00.000Z",
+        "resource_type": "Issue",
+        "resource_id": 555,
+        "label": {
+            "id": 100,
+            "name": "bug",
+            "color": "#FF0000",
+            "description": "Bug label"
+        },
+        "action": "add"
+    }"##;
+
+    let event: GitLabLabelEvent =
+        serde_json::from_str(json).expect("Failed to deserialize label event");
+
+    assert_eq!(event.id, 2001);
+    assert_eq!(event.action, "add");
+    assert_eq!(event.label.id, 100);
+    assert_eq!(event.label.name, "bug");
+    assert_eq!(event.label.color, Some("#FF0000".to_string()));
+    assert_eq!(event.label.description, Some("Bug label".to_string()));
+}
+
+#[test]
+fn deserializes_label_event_remove_null_color() {
+    let json = r#"{
+        "id": 2002,
+        "user": {
+            "id": 42,
+            "username": "developer",
+            "name": "Dev User"
+        },
+        "created_at": "2024-03-15T10:30:00.000Z",
+        "resource_type": "MergeRequest",
+        "resource_id": 777,
+        "label": {
+            "id": 101,
+            "name": "needs-review",
+            "color": null,
+            "description": null
+        },
+        "action": "remove"
+    }"#;
+
+    let event: GitLabLabelEvent =
+        serde_json::from_str(json).expect("Failed to deserialize label remove event");
+
+    assert_eq!(event.action, "remove");
+    assert!(event.label.color.is_none());
+    assert!(event.label.description.is_none());
+}
+
+#[test]
+fn deserializes_milestone_event() {
+    let json = r#"{
+        "id": 3001,
+        "user": {
+            "id": 42,
+            "username": "developer",
+            "name": "Dev User"
+        },
+        "created_at": "2024-03-15T10:30:00.000Z",
+        "resource_type": "Issue",
+        "resource_id": 555,
+        "milestone": {
+            "id": 200,
+            "iid": 5,
+            "title": "v1.0"
+        },
+        "action": "add"
+    }"#;
+
+    let event: GitLabMilestoneEvent =
+        serde_json::from_str(json).expect("Failed to deserialize milestone event");
+
+    assert_eq!(event.id, 3001);
+    assert_eq!(event.action, "add");
+    assert_eq!(event.milestone.id, 200);
+    assert_eq!(event.milestone.iid, 5);
+    assert_eq!(event.milestone.title, "v1.0");
+}
+
+#[test]
+fn deserializes_merge_request_ref() {
+    let json = r#"{
+        "iid": 42,
+        "title": "Feature branch",
+        "web_url": "https://gitlab.example.com/group/project/-/merge_requests/42"
+    }"#;
+
+    let mr_ref: GitLabMergeRequestRef =
+        serde_json::from_str(json).expect("Failed to deserialize MR ref");
+
+    assert_eq!(mr_ref.iid, 42);
+    assert_eq!(mr_ref.title, Some("Feature branch".to_string()));
+    assert_eq!(
+        mr_ref.web_url,
+        Some("https://gitlab.example.com/group/project/-/merge_requests/42".to_string())
+    );
+}
+
+#[test]
+fn deserializes_label_ref() {
+    let json = r##"{
+        "id": 100,
+        "name": "bug",
+        "color": "#FF0000",
+        "description": "Bug label"
+    }"##;
+
+    let label_ref: GitLabLabelRef =
+        serde_json::from_str(json).expect("Failed to deserialize label ref");
+
+    assert_eq!(label_ref.id, 100);
+    assert_eq!(label_ref.name, "bug");
+    assert_eq!(label_ref.color, Some("#FF0000".to_string()));
+}
+
+#[test]
+fn deserializes_milestone_ref() {
+    let json = r#"{
+        "id": 200,
+        "iid": 5,
+        "title": "v1.0"
+    }"#;
+
+    let ms_ref: GitLabMilestoneRef =
+        serde_json::from_str(json).expect("Failed to deserialize milestone ref");
+
+    assert_eq!(ms_ref.id, 200);
+    assert_eq!(ms_ref.iid, 5);
+    assert_eq!(ms_ref.title, "v1.0");
+}