Add related cases and duplicate review suggestions

src/lib/server/moderation/schema.ts

@@ -179,3 +179,26 @@ export function migrateModerationCaseAssessments(handle: Database.Database): voi
         );
     `);
 }
+
+export function migrateModerationCaseRelationships(handle: Database.Database): void {
+    handle.exec(`
+        CREATE TABLE IF NOT EXISTS moderation_case_relationships (
+            id TEXT PRIMARY KEY,
+            case_id TEXT NOT NULL REFERENCES moderation_cases(id),
+            target_case_id TEXT NOT NULL REFERENCES moderation_cases(id),
+            relation TEXT NOT NULL CHECK(relation IN ('same_incident','appeal_of','duplicate_of')),
+            actor_id TEXT NOT NULL,
+            actor TEXT NOT NULL,
+            created_at TEXT NOT NULL,
+            removed_at TEXT,
+            CHECK(case_id != target_case_id),
+            CHECK(relation != 'same_incident' OR case_id < target_case_id)
+        );
+        CREATE UNIQUE INDEX IF NOT EXISTS moderation_case_relationship_active
+            ON moderation_case_relationships(case_id,target_case_id,relation) WHERE removed_at IS NULL;
+        CREATE INDEX IF NOT EXISTS moderation_case_relationship_target
+            ON moderation_case_relationships(target_case_id,removed_at);
+        CREATE INDEX IF NOT EXISTS moderation_case_subject_recent
+            ON moderation_cases(game,guid,updated_at DESC,id);
+    `);
+}