[stable30] fx(dav): file request guest nickname encoding

[backportbot[bot]]

Backport of #49226

Warning, This backport's changes differ from the original and might be incomplete ⚠️

Todo

• [x] Review and resolve any conflicts

• [x] Remove all the empty commits

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.