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/api/routes/syndarix/test_issues.py

@@ -108,7 +108,9 @@ class TestCreateIssue:
         assert "urgent" in data["labels"]
         assert "frontend" in data["labels"]
 
-    async def test_create_issue_with_story_points(self, client, user_token, test_project):
+    async def test_create_issue_with_story_points(
+        self, client, user_token, test_project
+    ):
         """Test creating issue with story points."""
         project_id = test_project["id"]
 
@@ -237,7 +239,9 @@ class TestListIssues:
         assert len(data["data"]) == 1
         assert data["data"][0]["status"] == "open"
 
-    async def test_list_issues_filter_by_priority(self, client, user_token, test_project):
+    async def test_list_issues_filter_by_priority(
+        self, client, user_token, test_project
+    ):
         """Test filtering issues by priority."""
         project_id = test_project["id"]
 
@@ -703,7 +707,9 @@ class TestIssueAssignment:
 
         assert response.status_code == status.HTTP_404_NOT_FOUND
 
-    async def test_assign_issue_clears_assignment(self, client, user_token, test_project):
+    async def test_assign_issue_clears_assignment(
+        self, client, user_token, test_project
+    ):
         """Test that assigning to null clears both assignments."""
         project_id = test_project["id"]
 
@@ -890,7 +896,9 @@ class TestIssueCrossProjectValidation:
 class TestIssueValidation:
     """Tests for issue validation during create/update."""
 
-    async def test_create_issue_invalid_priority(self, client, user_token, test_project):
+    async def test_create_issue_invalid_priority(
+        self, client, user_token, test_project
+    ):
         """Test creating issue with invalid priority."""
         project_id = test_project["id"]
 
@@ -922,7 +930,9 @@ class TestIssueValidation:
 
         assert response.status_code == status.HTTP_422_UNPROCESSABLE_ENTITY
 
-    async def test_update_issue_invalid_priority(self, client, user_token, test_project):
+    async def test_update_issue_invalid_priority(
+        self, client, user_token, test_project
+    ):
         """Test updating issue with invalid priority."""
         project_id = test_project["id"]