Add Product to the ZGW API registration

[robinmolen]

Closes #4796

Changes

Added product as a configuration option to the ZGW API registration. The product select gets populated from the selected case type. If there are multiple versions of the case type, then the case type version that is active at the moment of configuring is chosen.

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 91.07143% with 5 lines in your changes missing coverage. Please review.

Project coverage is 96.57%. Comparing base (77e2cd6) to head (a50050b).
Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
src/openforms/contrib/zgw/products_and_services.py	75.00%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4803      +/-   ##
==========================================
- Coverage   96.58%   96.57%   -0.01%     
==========================================
  Files         748      749       +1     
  Lines       25477    25531      +54     
  Branches     3368     3376       +8     
==========================================
+ Hits        24606    24656      +50     
- Misses        608      612       +4     
  Partials      263      263              

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[sergei-maertens]

I'd suggest renaming product -> product_url everywhere so that it's clear we're dealing with a URL. Especially because we're moving literal URL-configuration options to their semantic 'description' and resolve URLs dynamically, I suspect we will go through this at some point too (where maybe a product slug/description will be stored instead of the exact URL).

[sergei-maertens]

Can you address this type checker error? I would opt to make the key required in the product, if it's missing from the upstream API, you can default it to an empty string.

[sergei-maertens]

I'm not 100% happy with how the catalogueUrl now is passed around/calculated, but I won't let it block this PR since my #4606 UX ticket will touch that code anyway, so I'll play around with it in my future PR.

Once the type checking error is addressed, we can merge this.