Add support for live translations in calls

[danxuliu]

⚠️ ⚠️ ⚠️ ⚠️ ⚠️ WIP ⚠️ ⚠️ ⚠️ ⚠️ ⚠️

Talk side of nextcloud/live_transcription#54

Besides the live_transcription app note that https://github.com/nextcloud/translate2 (or any other app that provides translations) is needed.

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After
TODO	TODO

🚧 Tasks

• Add selector for preferred translation language in app settings
• Convert live transcription button to a split button to choose between the original transcription or a translated one
• Translations will be slower than transcriptions, so they could look broken to the user if nothing appears for quite some time; maybe the original transcription could still be shown dimmed/transparent so the user sees that something is happening and then it is replaced by the translated text in full opacity once available - Most likely a follow up once this got some testing with a real server, and this will require changes in the live_transcription app, because once translations are enabled they fully replace transcriptions, so the transcription is no longer available

🏁 Checklist

• 🌏 Tested with different browsers / clients:
  • Chromium (Chrome / Edge / Opera / Brave)
  • Firefox
  • Safari
  • Talk Desktop
  • Integrations with Files sidebar and other apps
  • Not risky to browser differences / client
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

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🛠️ API Checklist

🚧 Tasks

• Capability is not fully reliable, as the capabilities of live_transcription app can not be got from Talk. For now it is checked whether the translation tasks are available, but that could return a false positive if the live_transcription app is installed but it is an old version that did not support translations.
• Better error handling, as right now setting the target language may not always fail with a bad request but an internal error if translations are not available in the live_transcription app
• Endpoints might require tweaking based on the UI development

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not possible
• 📘 API documentation in docs/ has been updated or is not required
• 🔖 Capability is added or not needed