Added Identifier to base and implementation

app/providers/base.py

@@ -88,7 +88,15 @@ class MusicProviderClient(ABC):
     """
     Abstract base class defining the interface for music provider clients.
     """
-
+    @property
+    @abstractmethod
+    def _identifier(self) -> str:
+        """
+        A unique identifier for the music provider.
+        Must be implemented by all subclasses.
+        """
+        pass
+    
     @abstractmethod
     def authenticate(self, credentials: dict) -> None:
         """

app/providers/spotify.py

@@ -32,7 +32,10 @@ class SpotifyClient(MusicProviderClient):
     """
     Spotify implementation of the MusicProviderClient.
     """
-
+    @property
+    def _identifier(self) -> str:
+        return "Spotify"
+    
     def __init__(self, cookie_file: Optional[str] = None):
         self.base_url = "https://api-partner.spotify.com"
         self.session_data = None