Add backend routes and frontend service for admin CRUD of ModelRegistries

[mturley]

Closes https://issues.redhat.com/browse/RHOAIENG-7058

Description

Adds the following admin-only backend API routes:

• GET /api/modelRegistries - lists ModelRegistries
• POST /api/modelRegistries - creates a ModelRegistry
• GET /api/modelRegistries/:modelRegistryName - gets a ModelRegistry
• PATCH /api/modelRegistries/:modelRegistryName - updates a ModelRegistry
• DELETE /api/modelRegistries/:modelRegistryName - deletes a ModelRegistry

And adds the new frontend/src/services/modelRegistryService.ts with functions to call these routes using axios.

Also adds a new constant MODEL_REGISTRY_NAMESPACE to backend/src/utils/constants.ts since there are some places where we were hard-coding the use of the odh-model-registries namespace.

How Has This Been Tested?

The admin page where this will be used does not exist yet (it is being created in #2810). I tested the two GET routes by inserting this temporary code into another existing page:

  React.useEffect(() => {
    const fetchData = async () => {
      const registries = await listModelRegistriesBackend();
      console.log('Registries!', registries);
      const registry = await getModelRegistryBackend('internal-registry');
      console.log('Registry!', registry);
    };
    fetchData();
  }, []);

This worked as expected. I did not yet test the POST, PATCH or DELETE routes because I don't want to mess with what's currently set up on the shared cluster. Those will be tested as part of upcoming PRs to consume these routes, and any issues we find at that time can be addressed in those PRs.

Test Impact

No tests here currently. There are no existing tests for any of these backend routes or corresponding services. They are also a temporary workaround to be removed when we access these services via a passthrough API (per @lucferbux) so tests here would be removed soon anyway.

Request review criteria:

Self checklist (all need to be checked):

• The developer has manually tested the changes and verified that the changes work
• Commits have been squashed into descriptive, self-contained units of work (e.g. 'WIP' and 'Implements feedback' style messages have been removed)
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has added tests or explained why testing cannot be added (unit or cypress tests for related changes)

If you have UI changes:

• Included any necessary screenshots or gifs if it was a UI change.
• Included tags to the UX team if it was a UI/UX change (find relevant UX in the SMEs section).

After the PR is posted & before it merges:

• The developer has tested their solution on a cluster by using the image produced by the PR to main

[lucferbux]

Just add the permissions and I think it would be ready to go

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 33 lines in your changes are missing coverage. Please review.

Project coverage is 77.23%. Comparing base (8645fe6) to head (b5b8257).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2812      +/-   ##
==========================================
- Coverage   77.32%   77.23%   -0.09%     
==========================================
  Files        1093     1094       +1     
  Lines       23026    23059      +33     
  Branches     5799     5799              
==========================================
+ Hits        17805    17810       +5     
- Misses       5221     5249      +28     

Files	Coverage Δ
frontend/src/services/modelRegistryService.ts	0.00% <0.00%> (ø)

... and 3 files with indirect coverage changes

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[mturley]

@lucferbux @gitdallas I updated this to add the DELETE route, if you don't mind re-reviewing

[lucferbux]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gitdallas, lucferbux

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