feat: Allow WebP content type in PhotoCache

[st3iny]

• Resolves: Image not shown when using WebP instead of JPEG contacts#4190
• Closes Allow WebP and SVG content types in PhotoCache #48842

Summary

I recreated the PR in the repository to get green CI. I also tested it locally and it works fine.

It seems like CardDAV's PhotoCache is currently only supporting PNG, JPEG, GIF and ICO images.

Nextcloud intercepts GET requests on addressbook URLs ending with ?photo, and uses ALLOWED_CONTENT_TYPES to set the type name, returning 404 if the content type is not supported (not part of the allowed content types struct).

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)