- Methods should do one thing — follow the Single Responsibility Principle (SRP).
- Favor meaningful method and variable names that clearly express intent.
- Limit method parameters to 3 or fewer — use objects or builders for complex inputs.
- Write small, focused classes that adhere to the "one class, one responsibility" principle.
- Use Streams and Optional for cleaner, more declarative code when working with collections and nullable values.
- Prefer constructor injection over field injection for better testability and immutability.
- Use proper logging (e.g., SLF4J) instead of System.out.println().
- Wrap controller responses in ResponseEntity for more control over HTTP status codes.
- Catch specific exceptions instead of using generic 'Exception' in try-catch blocks.
- Use Lombok annotations like @Data, @Value, and @Builder to reduce boilerplate code.
- Keep controllers lean — delegate business logic to service classes.
- Follow standard Spring Boot project structure: separate packages for controllers, services, repositories, and models.
- Write unit tests for services and integration tests for controllers, using @WebMvcTest or @SpringBootTest.
- Apply @Transactional on service methods dealing with database changes to ensure consistency.

Analyze the code and error. Suggest and implement a fix using best practices.

Write tests following these guidelines:
- Add type hints for all fixture arguments.
- Use other similar test files as example to keep repository style consistent.

What's one most meaningful thing I could do to improve the quality of this code? It shouldn't be too drastic but should still improve the code.