Use the right l10n object if the template is loaded from another app

[jvillafanez]

Description

Some apps can include template parts from a different app, normally from core. From example, the activity app can include content from the core templates to be used in the activity email.
The translated strings where picked from the original app even though the template was loaded from core. As a result, some string weren't translated because the missing translation for those strings in the original app. Note that core had the string correctly translated.

Related Issue

https://github.com/owncloud/enterprise/issues/4249

Motivation and Context

How Has This Been Tested?

Manually tested with a custom theme, which loads some core content in the activity app.

Screenshots (if appropriate):

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

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

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

No Coverage information
No Duplication information