refactor(backend): reduce surface by unifying metadata endpoints

[matmair]

Replaces individual metadata endpoints with a generic endpoint and a bunch of permanent redirects. Obviously a breaking change.
This:

• reduces the amount of duplicated endpoints doing the same things and the required tests too
• removes the necessity to declare new endpoints for every metadata-supporting model
• is plugin friendly as models defined in those can also use the new endpoint

Requires a change to the client libary - inventree/inventree-python#285

[netlify]

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[codecov]

Codecov Report

❌ Patch coverage is 88.60759% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.16%. Comparing base (025f6ff) to head (fa03f9f).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #11035      +/-   ##
==========================================
- Coverage   88.18%   88.16%   -0.03%     
==========================================
  Files        1290     1290              
  Lines       58142    58145       +3     
  Branches     1969     1969              
==========================================
- Hits        51273    51264       -9     
- Misses       6378     6390      +12     
  Partials      491      491              

Flag	Coverage Δ
backend	89.46% <88.60%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Backend Apps	92.01% <100.00%> (-0.02%)	⬇️
Backend General	93.48% <100.00%> (ø)
Frontend	70.85% <ø> (ø)

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[codspeed-hq]

CodSpeed Performance Report

Merging #11035 will not alter performance

_{Comparing matmair:reduce-metadata-endpoints (fa03f9f) with master (025f6ff)¹}

Summary

✅ 2 untouched

Footnotes

1. No successful run was found on master (97ea76a) during the generation of this report, so 025f6ff was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[matmair]

@SchrodingersGat this is ready for review, the needed change for the API client is already proposed inventree/inventree-python#285

You can see the passing test with that branch in https://github.com/inventree/InvenTree/actions/runs/20733404036/job/59525935718

[SchrodingersGat]

@matmair this does look a lot cleaner.

To confirm what you are doing here - all metadata is accessed via /api/metadata/pk/ - but the existing URLs all continue to work via redirect?