Add EntityFacts to describedBy object

[acka47]

@felixlohmeier requested via email a way to query describedBy.dateModified and to also get the last modification date of data from EntityFacts. One option would be

1. to make describedBy an array (which would be an API break) and
2. to inject an object into describedBy for each resource that gets information from EntityFacts with dateModified of the last day we updated from EntityFacts.

E.g. for https://lobid.org/gnd/124767079:

{
  "describedBy":[
    {
      "id":"https://d-nb.info/gnd/124767079/about",
      "license":{
        "id":"http://creativecommons.org/publicdomain/zero/1.0/",
        "label":"http://creativecommons.org/publicdomain/zero/1.0/"
      },
      "dateModified":"2020-12-18T16:08:46.000"
    },
    {
      "id":"https://hub.culturegraph.org/entityfacts/124767079",
      "license":{
        "id":"http://creativecommons.org/publicdomain/zero/1.0/",
        "label":"http://creativecommons.org/publicdomain/zero/1.0/"
      },
      "dateModified":"2021-08-27"
    }
  ]
}

To clarify, we would update the dateModified with each update form EntityFacts although for most resources the EntityFacts information doesn't change between updates. @felixlohmeier, would this suit your use case?

[felixlohmeier]

Yes, that would solve my use case.I am looking for a way to pre-filter weekly bulk downloads to save resources.