fix(theming): make cache buster depend on the app version

[st3iny]

• Resolves: #

Summary

Due to the new design, many css variables changed. However, the cache buster value does not increase on Theming/Nextcloud upgrades which causes old theming stylesheets to remain cached. Thus, some apps on the Nextcloud instance look broken after an upgrade (to 30) until the cache is cleared.

How to reproduce?

1. Clear browser data, open dev tools and make sure to enable caching.
2. Install Nextcloud stable29 and Calendar stable4.7.
3. Disable debug mode in config.php!
4. Navigate to Calendar.
5. Upgrade Nextcloud to master and Calendar to main.
6. Upgrade your Nextcloud instance using occ.
7. Navigate to Calendar in a new tab.
8. Observe broken styling.
9. Clear cache and reload Calendar.
10. Observe working styling.

Between steps 7 and 9 you can also observe that the content of theming stylesheets changes but not their cache buster hash (?v=[...]).

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)

[ChristophWurst]

Makes sense

[AndyScherzinger]

🐘

[st3iny]

/backport to stable28

[st3iny]

/backport to stable29