* feat: add avatar download and upload functionality in authentication adapter
- Implemented `download_and_upload_avatar` method to fetch and store user avatars from OAuth providers.
- Enhanced user data saving process to include avatar handling.
- Updated `S3Storage` class with a new `upload_file` method for direct file uploads to S3.
* feat: enhance avatar download functionality with size limit checks
- Added checks for content length before downloading avatar images to ensure they do not exceed the maximum allowed size.
- Implemented chunked downloading of avatar images to handle large files efficiently.
- Updated the upload process to return None if the upload fails, improving error handling.
* feat: improve avatar filename generation with content type handling
- Refactored avatar download logic to determine file extension based on the content type from the response headers.
- Removed redundant code for extension mapping, ensuring a cleaner implementation.
- Enhanced error handling by returning None for unsupported content types.
* fix: remove authorization header for avatar download
- Updated the avatar download logic to remove the Authorization header when token data is not present, ensuring compatibility with scenarios where authentication is not required.
* feat: add method for avatar download headers
- Introduced `get_avatar_download_headers` method to centralize header management for avatar downloads.
- Updated `download_and_upload_avatar` method to utilize the new header method, improving code clarity and maintainability.
- Update S3Storage to use configurable expiration time
- Default remains 3600 seconds (1 hour) for backward compatibility
- Add comprehensive unit tests with mocked S3 client
- Update .env.example with documentation and examples
