[WIP] feat: file conversion provider

[elzody]

• Part of: 📄💫 File conversion #49603

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?

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)

[juliusknorr]

I'm still unsure if we rather should return either a stream or just a path to a temporary file here

[elzody]

Since we probably want this to work well with the workflow engine, maybe it would make more sense to return a file path. Maybe, if a target destination is passed to the API endpoint, we could convert the file with the appropriate conversion provider, then store the file there and return its location/metadata in the response. Or, if no destination is provided, we could just use a temporary location?

For the interfaces though, maybe it would rather make sense to leave them as they are, so if the providers are called another way (say from the same app which implements it) the developer could just use it however they like. But not sure how you want to go about it.

[juliusknorr]

Something i haven't thought about but we could also make the target mime types an array here, but no strong opinion here from my side.

[elzody]

Hmm, do you mean that, in the scenario where the provider can convert the same MIME type to multiple other MIME types, instead of registering multiple ConversionMimeTuples for the same original MIME type with different output MIME types, it would just be one and could have an array of output MIME types it can convert it to?