[FEATURE REQUEST] Always send a language header in all requests

[michaelstingl]

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

Latest oCIS notifications API (/ocs/v2.php/apps/notifications/api/v1/notifications?format=json) responds with translated content. Other endpoints will learn this too.

Describe the solution you'd like

Android app should always send a language header in all requests which follows the Accept-Language spec:

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Language

Describe alternatives you've considered

No response

Additional context

Related:

• Web: [web] Always send a language header in all requests web#8612
• Desktop: Always send a language header in all requests client#10619
• iOS: [FEATURE REQUEST] Always send a language header in all requests ios-app#1193

TASKS

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

PR

• App
• Library (if needed)