✨ [#4788] ConfigurationStep for Objects API registration config

[stevenbal]

Closes #4788
Closes #4787

TODO:

• add identifier field to ObjectsAPIGroupConfig and use that in step
• remove is_configured and validate_result
• update zgw_consumers config file

Depends on:

• Refactor core API based on Pydantic models and direct loading from external sources maykinmedia/django-setup-configuration#18
• ✨ [#100] Add ConfigurationStep for Service model maykinmedia/zgw-consumers#99

Changes

• ConfigurationStep for Objects API registration config

Checklist

Check off the items that are completed or not relevant.

• Impact on features

  • Checked copying a form
  • Checked import/export of a form
  • Config checks in the configuration overview admin page
  • Problem detection in the admin email digest is handled

• Release management

  • I have labelled the PR as "needs-backport" accordingly

• I have updated the translations assets (you do NOT need to provide translations)

  • Ran ./bin/makemessages_js.sh
  • Ran ./bin/compilemessages_js.sh

• Commit hygiene

  • Commit messages refer to the relevant Github issue
  • Commit messages explain the "why" of change, not the how

[codecov]

Codecov Report

Attention: Patch coverage is 98.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 96.56%. Comparing base (b5daa22) to head (a4fde34).
Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
src/openforms/config/setup_configuration/steps.py	97.87%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4822   +/-   ##
=======================================
  Coverage   96.55%   96.56%           
=======================================
  Files         748      750    +2     
  Lines       25417    25483   +66     
  Branches     3361     3372   +11     
=======================================
+ Hits        24542    24607   +65     
  Misses        610      610           
- Partials      265      266    +1     

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[stevenbal]

I wasn't entirely sure on what directory to place these files in, should they be in src/openforms/config/... or in src/openforms/contrib/...?

[sergei-maertens]

hrm, will have to have a think, I think it'll partly be both? e.g. 3rd party library stuff like zgw consumers in config, and openforms constructs (like objectsapigroup) in contrib close to where the models are defined.

This of course assumes such degree of modularity in django-setup-configuration

[stevenbal]

@sergei-maertens this PR of course depends on the changes in django-setup-configuration and zgw-consumers, but I figured it would be good if you could take a look at the implementation before I start working on #4789