feat: file conversion provider

[elzody]

• Part of: 📄💫 File conversion #49603
• Front: feat(api): File conversion Files action #50123

Summary

This PR will introduce a file conversion API endpoint, which can be called to convert a file from one type to another. Apps can register their own conversion providers (which implement IConversionProvider), and the providers can define which MIME types they support for conversion via ConversionMimeTuples.

TODO

• OpenAPI specs
• Flesh out some more details around the IConversionProvider interface
  • What type should it really return? Stream, resource, File, file path?
• What should happen when multiple apps register similar conversion providers?
• How should we make the preferred list of conversion providers?

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[provokateurin]

Very nice! I only have a few smaller things to not, feel free to ignore the most nit picky ones 😅

[provokateurin]

Wouldn't it make sense to also check that the threshold is a sensible value? Otherwise an admin might configure something like 100 GiB and break their instance. I'm not sure what a reasonable limit is, especially when it comes to high resolution photos or long (high resolution) videos.

[juliusknorr]

I don't see a risk of breaking the instance here. If an admin configures long timeouts then it should be fine. At some point we may rather want to have background workers that do an async conversion so we don't run into timeouts (which is the main reason for adding this), but this was discussed out of scope due to the short-term scheduling with @AndyScherzinger.

[juliusknorr]

It looks like this part is failing to serialize to xml in the integration tests, but have not checked locally, so not sure what the best way to fix this is.

{
  "reqId": "6YTbALAvT2hTLsT4X3ec",
  "level": 3,
  "time": "2025-01-14T22:43:50+00:00",
  "remoteAddr": "::1",
  "user": "admin",
  "app": "PHP",
  "method": "GET",
  "url": "/ocs/v1.php/cloud/capabilities",
  "message": "ValueError: XMLWriter::writeElement(): Argument #2 ($content) must be a valid element name, \"image/png\" given at /home/runner/actions-runner/_work/server/server/lib/private/AppFramework/OCS/BaseResponse.php#149",
  "userAgent": "GuzzleHttp/7",
  "version": "31.0.0.9",
  "data": {
    "app": "PHP"
  }
}

[provokateurin]

Hm yeah that is tricky, seems like / is forbidden as tag name (makes sense since it is part of the XML syntax).
The output format could be changed so that it's no longer used as a key but the entire data structure is a list and the source format is just a property of the objects in the list.

[skjnldsv]

As a followup, it would be nice to add some integration tests.
Should be easy to test :

• the api response on failure
• the proper new png file after the api conversion endpoint have been reached