feat: add iMip Request Handling

[SebastianKrupinski]

• Resolves: #8458
• Requires: https://github.com/nextcloud/server/pull/47826

Summary

• added iMip request handling to automatically update calendar events

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• [x] Tests (unit, integration, api and/or acceptance) are included
• [ ] Backports requested where applicable (ex: critical bugfixes)