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/conftest.py

@@ -159,7 +159,9 @@ async def test_agent_type_crud(async_test_db, agent_type_create_data):
 
 
 @pytest_asyncio.fixture
-async def test_agent_instance_crud(async_test_db, test_project_crud, test_agent_type_crud):
+async def test_agent_instance_crud(
+    async_test_db, test_project_crud, test_agent_type_crud
+):
     """Create a test agent instance in the database for CRUD tests."""
     _test_engine, AsyncTestingSessionLocal = async_test_db
     async with AsyncTestingSessionLocal() as session: