Hub Matter provenance attached to too many entries

Hey @j.broeder how did you create the "_hub" field?

I think "hub_matter" got linked to too many records.

Among many others I can not recall that we mapped or curated this one for instance:

https://gitlab.hzdr.de/hmc/hmc/cct-1-mapping/mapping_results/-/blob/dev/hmc_wide/2_metadata_standards/Health%20Level%207.json#L2