Ensure channel ID is set on move change to trash tree

[bjester]

Summary

Description of the change(s) you made

The trash tree root node doesn't have channel_id annotated on it, so when deleting resources which moves them to the trash tree, the corresponding change event was missing the channel_id since it relied on the destination node having it. This updates that logic to fallback to the source node's channel_id, which should only ever be the case for moving to the trash tree.

This also adds the channel ID to node creation, since as a side effect, creating a new topic/folder and then immediately trying to delete it would fail given the newly added defensive check that prevents unset channel_id on the change objet.

Manual verification steps performed

1. Create a topic
2. Delete a topic
3. Ensure the deletion change is allowed by the sync endpoint
4. Retry the above in quick succession

References

Fixes #3507

Comments

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[rtibbles]

Deletions were both allowed and successful, and did not reappear. Much rejoicing!