affiliations: switch to datastreams

[tmorrell]

:heart: Thank you for your contribution!

Description

This PR upgrades affiliation to a datastream and makes it consistent with funders and ROR v2 https://github.com/inveniosoftware/invenio-vocabularies/issues/318.

https://github.com/inveniosoftware/invenio-app-rdm/pull/2680 is needed for it to work within RDM

Checklist

Ticks in all boxes and 🟢 on all GitHub actions status checks are required to merge:

• [x] I'm aware of the code of conduct.
• [x] I've created logical separate commits and followed the commit message format.
• [x] I've added relevant test cases.
• [x] I've added relevant documentation.
• [x] I've marked translation strings.
• [x] I've identified the copyright holder(s) and updated copyright headers for touched files (>15 lines contributions).
• [x] I've NOT included third-party code (copy/pasted source code or new dependencies).
  • If you have added third-party code (copy/pasted or new dependencies), please reach out to an architect.

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[tmorrell]

You can test this locally by adding the following to your Pipfile:

invenio-app-rdm = {extras = ["opensearch2"], version = "~=13.0.0b0.dev1", git = "https://github.com/caltechlibrary/invenio-app-rdm.git", ref = "affiliation_datastream"}
invenio-vocabularies = {git = "https://github.com/caltechlibrary/invenio-vocabularies.git", ref = "affiliation_datastream"}