correct SQLModel typing

backend/app/db/models/tasks.py

@@ -3,7 +3,7 @@ from typing import Optional
 from datetime import datetime
 from uuid import UUID, uuid4
 
-from sqlalchemy import Enum
+from sqlalchemy import Column, Enum
 from sqlalchemy.orm import Mapped, mapped_column
 from sqlmodel import SQLModel, Field, Relationship
 
@@ -27,7 +27,19 @@ class Task(SQLModel, table=True):
     service: Optional[str] = None
     updated_at: datetime = Field(default_factory=datetime.utcnow)
 
-    source: Mapped[Optional[SourceEnum]] = mapped_column(Enum(SourceEnum))
+    # source: Mapped[Optional[SourceEnum]] = mapped_column(Enum(SourceEnum)) <- SQLAlchemy not SQLModel
+
+    source: Optional[SourceEnum] = Field(
+        default=None,
+        sa_column=Column(
+            Enum(
+                SourceEnum,
+                name="source",
+                values_callable=lambda e: [m.value for m in e],
+            ),
+            nullable=True,
+        ),
+    )
     source_id: Optional[str] = None
 
     sub_tasks: list["SubTask"] = Relationship(back_populates="task")