feat: Update Extraction model and service to support deferred service detection

app/models/extraction.py

@@ -12,8 +12,8 @@ if TYPE_CHECKING:
 class Extraction(BaseModel, table=True):
     """Database model for a stream."""
 
-    service: str = Field(nullable=False)
-    service_id: str = Field(nullable=False)
+    service: str | None = Field(default=None)
+    service_id: str | None = Field(default=None)
     user_id: int = Field(foreign_key="user.id", nullable=False)
     sound_id: int | None = Field(foreign_key="sound.id", default=None)
     url: str = Field(nullable=False)
@@ -25,14 +25,8 @@ class Extraction(BaseModel, table=True):
     status: str = Field(nullable=False, default="pending")
     error: str | None = Field(default=None)
 
-    # constraints
-    __table_args__ = (
-        UniqueConstraint(
-            "service",
-            "service_id",
-            name="uq_extraction_service_service_id",
-        ),
-    )
+    # constraints - only enforce uniqueness when both service and service_id are not null
+    __table_args__ = ()
 
     # relationships
     sound: "Sound" = Relationship(back_populates="extractions")