feat: update owner column to be nullable in tasks and push notification config tables

Author: sokoliva

src/a2a/migrations/versions/6419d2d130f6_add_columns_owner_last_updated.py

@@ -47,7 +47,7 @@ def upgrade() -> None:
     )
 
     if table_exists(tasks_table):
-        add_column(tasks_table, 'owner', False, sa.String(255), owner)
+        add_column(tasks_table, 'owner', True, sa.String(255), owner)
         add_column(tasks_table, 'last_updated', True, sa.DateTime())
         add_index(
             tasks_table,
@@ -63,7 +63,7 @@ def upgrade() -> None:
         add_column(
             push_notification_configs_table,
             'owner',
-            False,
+            True,
             sa.String(255),
             owner,
         )

src/a2a/server/models.py

@@ -44,7 +44,7 @@ class TaskMixin:
     kind: Mapped[str] = mapped_column(
         String(16), nullable=False, default='task'
     )
-    owner: Mapped[str] = mapped_column(String(255), nullable=False)
+    owner: Mapped[str] = mapped_column(String(255), nullable=True)
     last_updated: Mapped[datetime | None] = mapped_column(
         DateTime, nullable=True
     )
@@ -145,7 +145,7 @@ class PushNotificationConfigMixin:
     task_id: Mapped[str] = mapped_column(String(36), primary_key=True)
     config_id: Mapped[str] = mapped_column(String(255), primary_key=True)
     config_data: Mapped[bytes] = mapped_column(LargeBinary, nullable=False)
-    owner: Mapped[str] = mapped_column(String(255), nullable=False, index=True)
+    owner: Mapped[str] = mapped_column(String(255), nullable=True, index=True)
     protocol_version: Mapped[str | None] = mapped_column(
         String(16), nullable=True
     )