Add custom apps translation scripts and image path for consistency

[akhil1508]

• Resolves: Custom apps translation and image asset handling is not consistent with core apps #40897

Summary

• Add checks for custom app translations and images

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[kesselb]

I'm unsure about this change in general.
I have plenty of apps in apps-extra and see the requests for the translation files.

[akhil1508]

I'm unsure about this change in general.
I have plenty of apps in apps-extra and see the requests for the translation files.

For me, occ app:install calendar installed it in custom_apps folder. I don't see the requests for custom_apps/calendar/l10n/$lang.js for any language. Nor if I modify via theme..

Ah I recall now it is set through the apps_paths config

[kesselb]

@juliushaertl @skjnldsv I'm totally unsure if the patch makes sense, we need it, etc .. 🙈

However, I dislike the ability to modify files from apps via a theme.

[juliushaertl]

I'm all in for dropping the theme generally once we have proper ways to achieve its mainly used functionality otherwise #27433

I think for now the change makes sense, to ensure that the legacy theme mechanism works as expected with custom app paths.

[juliushaertl]

Would be good to squash the commits into one, otherwise this seems good.

[akhil1508]

Would be good to squash the commits into one

@juliushaertl Squashed

[juliushaertl]

Failures seem unrelated.