Arvados

Child containers are determined by querying for container requests where requested_by_container_uuid matches the parent container. This does not work for federated workflows, because (a) containers run on remote clusters don't set requested_by_container_uuid and (b) even if it was set, we don't have an easy way to query remotes (requires either #14374 or generalizing javascript multi-site search feature).

Solution:

1. When controller creates a remote container request, it can supply requested_by_container_uuid
2. Controller records the uuid of the remote container request, and saves a cache copy of container request record in the local database with the appropriate requested_by_container_uuid
3. The client can filter on requested_by_container_uuid in the local database and get both local and remote container requests.
4. When a client makes a list or get request that returns remote objects, fetch the latest records from the remote cluster and merge the updated records into the response. (And update the cached copy?)

What should the owner_uuid by on the cache copy?