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.

tests/conftest.py

@@ -335,5 +335,3 @@ async def admin_cookies(admin_user: User) -> dict[str, str]:
     access_token = JWTUtils.create_access_token(token_data)
 
     return {"access_token": access_token}
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