Override browser locales with OC locale in ajax requests

[VicDeo]

Description

Send Accept-Language header based on the current OC user locale

Related Issue

• Fixes https://github.com/owncloud/enterprise/issues/4159

Motivation and Context

owncloud API uses Accept-Language header to set the response locale. This PR overrides a default Accept-Language sent by browser with the current user locale

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:
• Changelog item, see TEMPLATE

[phil-davis]

There were silly drone/docker errors. I rebased to get fresh CI.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
No Duplication information