test(backend): add comprehensive tests for OAuth and agent endpoints

- Added tests for OAuth provider admin and consent endpoints covering edge cases.
- Extended agent-related tests to handle incorrect project associations and lifecycle state transitions.
- Introduced tests for sprint status transitions and validation checks.
- Improved multiline formatting consistency across all test functions.

backend/tests/crud/syndarix/test_sprint_crud.py

@@ -121,7 +121,9 @@ class TestSprintUpdate:
                 name="Updated Sprint Name",
                 goal="Updated goal",
             )
-            result = await sprint_crud.update(session, db_obj=sprint, obj_in=update_data)
+            result = await sprint_crud.update(
+                session, db_obj=sprint, obj_in=update_data
+            )
 
             assert result.name == "Updated Sprint Name"
             assert result.goal == "Updated goal"
@@ -139,7 +141,9 @@ class TestSprintUpdate:
                 start_date=today + timedelta(days=1),
                 end_date=today + timedelta(days=21),
             )
-            result = await sprint_crud.update(session, db_obj=sprint, obj_in=update_data)
+            result = await sprint_crud.update(
+                session, db_obj=sprint, obj_in=update_data
+            )
 
             assert result.start_date == today + timedelta(days=1)
             assert result.end_date == today + timedelta(days=21)
@@ -163,7 +167,9 @@ class TestSprintLifecycle:
             assert result.status == SprintStatus.ACTIVE
 
     @pytest.mark.asyncio
-    async def test_start_sprint_with_custom_date(self, async_test_db, test_project_crud):
+    async def test_start_sprint_with_custom_date(
+        self, async_test_db, test_project_crud
+    ):
         """Test starting sprint with custom start date."""
         _test_engine, AsyncTestingSessionLocal = async_test_db
 
@@ -195,7 +201,9 @@ class TestSprintLifecycle:
             assert result.start_date == new_start
 
     @pytest.mark.asyncio
-    async def test_start_sprint_already_active_fails(self, async_test_db, test_project_crud):
+    async def test_start_sprint_already_active_fails(
+        self, async_test_db, test_project_crud
+    ):
         """Test starting an already active sprint raises ValueError."""
         _test_engine, AsyncTestingSessionLocal = async_test_db
 
@@ -250,7 +258,9 @@ class TestSprintLifecycle:
             assert result.status == SprintStatus.COMPLETED
 
     @pytest.mark.asyncio
-    async def test_complete_planned_sprint_fails(self, async_test_db, test_project_crud):
+    async def test_complete_planned_sprint_fails(
+        self, async_test_db, test_project_crud
+    ):
         """Test completing a planned sprint raises ValueError."""
         _test_engine, AsyncTestingSessionLocal = async_test_db
 
@@ -300,7 +310,9 @@ class TestSprintLifecycle:
             assert result.status == SprintStatus.CANCELLED
 
     @pytest.mark.asyncio
-    async def test_cancel_completed_sprint_fails(self, async_test_db, test_project_crud):
+    async def test_cancel_completed_sprint_fails(
+        self, async_test_db, test_project_crud
+    ):
         """Test cancelling a completed sprint raises ValueError."""
         _test_engine, AsyncTestingSessionLocal = async_test_db
 
@@ -329,7 +341,9 @@ class TestSprintByProject:
     """Tests for getting sprints by project."""
 
     @pytest.mark.asyncio
-    async def test_get_by_project(self, async_test_db, test_project_crud, test_sprint_crud):
+    async def test_get_by_project(
+        self, async_test_db, test_project_crud, test_sprint_crud
+    ):
         """Test getting sprints by project."""
         _test_engine, AsyncTestingSessionLocal = async_test_db
 
@@ -506,7 +520,9 @@ class TestSprintWithIssueCounts:
     """Tests for getting sprints with issue counts."""
 
     @pytest.mark.asyncio
-    async def test_get_sprints_with_issue_counts(self, async_test_db, test_project_crud, test_sprint_crud):
+    async def test_get_sprints_with_issue_counts(
+        self, async_test_db, test_project_crud, test_sprint_crud
+    ):
         """Test getting sprints with issue counts."""
         _test_engine, AsyncTestingSessionLocal = async_test_db