api/v2/pretranslate cannot be used from the UI

[flodolo]

It should be possible to test api/v2/pretranslate via the UI, right now the parameters are not available.

1. Create a user part of the pretranslators group, create a PAT
2. Go to http://localhost:8000/api/v2/
3. Authorize with the PATH in the top right corner
4. Test the /pretranslate API