By using the claim, we can avoid leaking the PostgreSQL backups if a
user has a nextcloud instance.

It's now possible to list Nextcloud backups via the apiserver.
The backups will show both information, Nextcloud and PostgreSQL. It
will also show if the backup contains both Nextcloud and PostgreSQL
backups.

It was a bit on the low side and sometimes triggered timeouts on local
runs.

We're operating on the claim during the comp functions. For 99% of cases
this doesn't matter.

However if we accidentally add a field that's only in the claim to the
composite, then Crossplane will not like it.

So we remove the spec from the desired composite when we return the
response. As Crossplane only allows to update the `.metadata` and
`.status` objects.

It might result in an empty spec if there are multiple functions
in the composition. However this was not tested.