docs: update imports to use public diracx.tasks.depends module

Update documentation examples to import NoTransaction and
CallbackSpawner from diracx.tasks.depends instead of reaching
into diracx.tasks.plumbing.depends. Also add CallbackSpawner
to the public re-export.

Author: chrisburr

diracx-tasks/src/diracx/tasks/depends.py

@@ -2,6 +2,6 @@
 
 from __future__ import annotations
 
-from diracx.tasks.plumbing.depends import NoTransaction
+from diracx.tasks.plumbing.depends import CallbackSpawner, NoTransaction
 
-__all__ = ("NoTransaction",)
+__all__ = ("CallbackSpawner", "NoTransaction")

docs/dev/how-to/use-task-callbacks.md

@@ -7,7 +7,7 @@ The callback system provides a fan-out/fan-in pattern: spawn multiple child task
 Use `CallbackSpawner` to schedule children and a callback together:
 
 ```python
-from diracx.tasks.plumbing.depends import CallbackSpawner
+from diracx.tasks.depends import CallbackSpawner
 
 
 class OrchestrationTask(BaseTask):
@@ -40,7 +40,7 @@ The children are scheduled immediately. When the last child completes, the worke
 `CallbackSpawner` is a dependency injection type resolved by the worker. Declare it as a typed parameter in `execute()`:
 
 ```python
-from diracx.tasks.plumbing.depends import CallbackSpawner
+from diracx.tasks.depends import CallbackSpawner
 
 
 class MyTask(BaseTask):

docs/dev/reference/dependency-injection.md

@@ -104,7 +104,7 @@ For cases where a database connection is needed without a transaction (e.g., a t
 from typing import Annotated
 
 from diracx.db.sql import SandboxMetadataDB
-from diracx.tasks.plumbing.depends import NoTransaction
+from diracx.tasks.depends import NoTransaction
 
 
 async def execute(