Add support for private Deezer playlists using GW API

[geekinsanemx]

This adds automatic fallback to Deezer's Gateway API when accessing private/user playlists, enabling downloads of your own private playlists using your ARL token.

What was happening

Private playlists failed with PermissionException when trying to download: "An active access token must be used to query information about the current user"

This happened even with a valid ARL token because the public API doesn't support private playlists, only the Gateway (GW) API does.

Why it happened

Streamrip only used Deezer's public API (client.api.) which requires OAuth tokens for private content. The ARL token works with the Gateway API (client.gw.) but wasn't being used for playlists.

What changed

Added automatic GW API fallback in get_playlist() method:

1. First tries public API (works for public playlists)
2. If PermissionException occurs, automatically tries GW API
3. Converts GW API response format to match public API format
4. Handles private playlist quirks (CURATOR as bool vs dict)

New helper method _convert_gw_playlist_to_api_format() transforms:

• Uppercase GW keys (DATA, SONGS) to lowercase (data, tracks)
• Private playlist creator info from PARENT_USER fields
• Picture URLs from hashes to full CDN URLs

Result

Users can now download their private Deezer playlists seamlessly with their ARL token. Public playlists continue to work as before. If both APIs fail, users get clear error messages explaining:

• Possible causes (invalid ARL, restricted playlist, deleted playlist)
• Workaround (temporarily make playlist public)

Files modified:

• streamrip/client/deezer.py:
  • Import PermissionException from deezer.errors
  • Wrap get_playlist() with try/except for GW API fallback
  • Add _convert_gw_playlist_to_api_format() helper method
  • Add detailed error logging for troubleshooting

Tested with private playlists - successfully fetches metadata and tracks.