Add Spotify integration with improved token management and user interface

- Implemented Spotify OAuth handling in spotify_client_manager.py to ensure valid access tokens for users.
- Created helper functions in spotify_helper.py for refreshing tokens and retrieving user information.
- Developed manage_spotify.html template for connecting and managing Spotify accounts, displaying connection status and token information.
- Added logging for token management processes to enhance debugging and monitoring.
- Introduced a debug client for Spotify interactions to facilitate easier testing and development.

musicround/models.py

@@ -57,7 +57,7 @@ class User(db.Model, UserMixin):
     auth_provider = db.Column(db.String(20), default='local')  # 'local', 'google', 'authentik'
     
     # OAuth provider info - Spotify
-    oauth_id = db.Column(db.String(100))       # Spotify user ID
+    spotify_id = db.Column(db.String(100), index=True, unique=True, nullable=True) # Spotify user ID
     spotify_token = db.Column(db.Text)         # Store Spotify access token 
     spotify_refresh_token = db.Column(db.Text)  # Store Spotify refresh token
     spotify_token_expiry = db.Column(db.DateTime)