Refactor user endpoint tests to include pagination and response structure validation

- Updated tests for listing users to validate pagination and response format.
- Changed mock return values to include total count and pagination details.
- Refactored user creation mocks for clarity and consistency.
- Enhanced assertions to check for presence of pagination fields in responses.
- Adjusted test cases for user retrieval and updates to ensure proper handling of user data.
- Improved readability by restructuring mock definitions and assertions across various test files.

app/services/dashboard.py

@@ -72,9 +72,7 @@ class DashboardService:
                     "play_count": sound["play_count"],
                     "duration": sound["duration"],
                     "created_at": (
-                        sound["created_at"].isoformat()
-                        if sound["created_at"]
-                        else None
+                        sound["created_at"].isoformat() if sound["created_at"] else None
                     ),
                 }
                 for sound in top_sounds