📝 Add docstring to `needs_api_key` decorator

[arcane-engine[bot]]

This PR adds a detailed docstring to the needs_api_key decorator, enhancing code documentation and clarity for future developers.

Key Changes

• Documentation 📚
  • Added a comprehensive docstring to the needs_api_key decorator in studio/decorators.py.
  • The docstring explains the decorator's functionality, including its purpose, actions performed, and arguments.

These changes improve the maintainability and readability of the code by providing clear documentation for the needs_api_key decorator.