Add command to clear dav's photo cache

[kesselb]

Summary

Contacts is using a request like below to fetch the photo for a user from the vcard.

/remote.php/dav/addressbooks/users/alice/z-server-generated--system/Database:jane.vcf?photo

As fetching and parsing vcards might be expensive there's a cache for the photos in app-data. While there are event listeners in place to reset the cache for a vcard on update or delete, there might be still cases where it's helpful to clear the cache.

How to test:

• Make sure you have some contacts
• Open contacts
• Check oc_filecache for paths like '%dav-photocache%'
• Run the occ command
• Check oc_filecache for paths like '%dav-photocache%'
• Open contacts
• Check oc_filecache for paths like '%dav-photocache%'

Backports:

Only the command, refactoring is for 32.

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)

[hamza221]

Tested and works

[kesselb]

/backport 8a1ae09 to stable31

[kesselb]

/backport 8a1ae09 to stable30