[FEATURE REQUEST] Support "per app" language change on Android 13+

[michaelstingl]

Is your feature request related to a problem? Please describe.

I'd like to easily see the ownCloud Android app in different languages, for example to contribute to the translations, or to capture screenshots for tutorials etc

Describe the solution you'd like

Android 13+ supports the change of the language for an individual app in your device settings.

Describe alternatives you've considered

Currently, I need to switch the device language, what causes more friction.

Additional context

• https://support.google.com/android/answer/12395118
• https://developer.android.com/guide/topics/resources/app-languages

TASKS

• Research (if needed)
• Create branch feature/feature_language_android13
• Development tasks
  • Implement whatever
  • ...
• Code review and apply changes requested
• Design test plan
• QA
• Merge branch feature/feature_language_android13 into master

PR

• App
• Library (if needed)

[JuancaG05]

This shouldn't be so complex, it seems this feature can be included in the app by creating a new file specifying the languages we want to appear in this new device's settings menu, and then referencing it from the manifest. Let's say we could develop this in 2-3 days, taking into account QA?

[Aitorbp]

Hello @michaelstingl,
How many languages ​​do we put in the app? Right now I have included: English, Spanish, German, French ,Japanese and Chinese.

[michaelstingl]

In other repos, new languages gets added automatically when they reach a certain coverage threshold in Transifex.

Looks like plenty of languages?
https://github.com/owncloud/android/blob/master/.tx/config

@hosy @dschmidt @fmoc could you provide any pointers?