feat: Implement favorites management API; add endpoints for adding, removing, and retrieving favorites for sounds and playlists

feat: Create Favorite model and repository for managing user favorites in the database
feat: Add FavoriteService to handle business logic for favorites management
feat: Enhance Playlist and Sound response schemas to include favorite indicators and counts
refactor: Update API routes to include favorites functionality in playlists and sounds

app/models/favorite.py

@@ -0,0 +1,29 @@
+from typing import TYPE_CHECKING
+
+from sqlmodel import Field, Relationship, UniqueConstraint
+
+from app.models.base import BaseModel
+
+if TYPE_CHECKING:
+    from app.models.playlist import Playlist
+    from app.models.sound import Sound
+    from app.models.user import User
+
+
+class Favorite(BaseModel, table=True):
+    """Database model for user favorites (sounds and playlists)."""
+
+    user_id: int = Field(foreign_key="user.id", nullable=False)
+    sound_id: int | None = Field(foreign_key="sound.id", default=None)
+    playlist_id: int | None = Field(foreign_key="playlist.id", default=None)
+
+    # constraints
+    __table_args__ = (
+        UniqueConstraint("user_id", "sound_id", name="uq_favorite_user_sound"),
+        UniqueConstraint("user_id", "playlist_id", name="uq_favorite_user_playlist"),
+    )
+
+    # relationships
+    user: "User" = Relationship(back_populates="favorites")
+    sound: "Sound" = Relationship(back_populates="favorites")
+    playlist: "Playlist" = Relationship(back_populates="favorites")

app/models/playlist.py

@@ -5,6 +5,7 @@ from sqlmodel import Field, Relationship
 from app.models.base import BaseModel
 
 if TYPE_CHECKING:
+    from app.models.favorite import Favorite
     from app.models.playlist_sound import PlaylistSound
     from app.models.user import User
 
@@ -23,3 +24,4 @@ class Playlist(BaseModel, table=True):
     # relationships
     user: "User" = Relationship(back_populates="playlists")
     playlist_sounds: list["PlaylistSound"] = Relationship(back_populates="playlist")
+    favorites: list["Favorite"] = Relationship(back_populates="playlist")

app/models/sound.py

@@ -6,6 +6,7 @@ from app.models.base import BaseModel
 
 if TYPE_CHECKING:
     from app.models.extraction import Extraction
+    from app.models.favorite import Favorite
     from app.models.playlist_sound import PlaylistSound
     from app.models.sound_played import SoundPlayed
 
@@ -36,3 +37,4 @@ class Sound(BaseModel, table=True):
     playlist_sounds: list["PlaylistSound"] = Relationship(back_populates="sound")
     extractions: list["Extraction"] = Relationship(back_populates="sound")
     play_history: list["SoundPlayed"] = Relationship(back_populates="sound")
+    favorites: list["Favorite"] = Relationship(back_populates="sound")

app/models/user.py

@@ -8,6 +8,7 @@ from app.models.base import BaseModel
 if TYPE_CHECKING:
     from app.models.credit_transaction import CreditTransaction
     from app.models.extraction import Extraction
+    from app.models.favorite import Favorite
     from app.models.plan import Plan
     from app.models.playlist import Playlist
     from app.models.sound_played import SoundPlayed
@@ -37,3 +38,4 @@ class User(BaseModel, table=True):
     sounds_played: list["SoundPlayed"] = Relationship(back_populates="user")
     extractions: list["Extraction"] = Relationship(back_populates="user")
     credit_transactions: list["CreditTransaction"] = Relationship(back_populates="user")
+    favorites: list["Favorite"] = Relationship(back_populates="user")