Add scheduling availability settings

[ChristophWurst]

Fixes #27422

This is an early prototype for #27422

To do

• Fetch current availability value form the scheduling inbox via a propfind
• Ability to select a timezone
  • Auto-detect default via jstz
• Ability to add another slot for a day
• Ability to remove a slot from a day, but not the last one
• Prop patch the scheduling inbox with the updated availability rrule
• Start the week at Mo/Su depending on locale

Steps to test

• Open the new settings
• Set some slots where you want to be available and save them
• Open the Calendar app
• Create an event, invite another user or email address and open the free/busy view
• You should see anything outside the availability slots as out of office (screenshot above)

Ref https://datatracker.ietf.org/doc/html/rfc7953

Follow-ups

• Deduplicate slots into blocked AVAILABLE components if possible, e.g. when 9-5 is used five days a week
• Read and write time zone ID when updating CalDAV availability #29318 Save and restore selected timezone as a component in the VAVAILABILITY
• CalDAV availibility settings design polishing #29319 Possible design polishing
• Error handling of unprocessible VAVAILABILITY values set by other applications

[ChristophWurst]

@jancborchardt @nimishavijay what do you think about the design? Would this be acceptable as a first version?

One element missing from the screenshot above is the timezone picker. I guess that has to be above or below the daily pickers.

[twlawrenceko]

Hello, I do not see the groupware option under Personal section. Currently on 21.0.4. Does this functionality require mail, contacts, calendars app installed and configured?

Thank you

[ChristophWurst]

Hello, I do not see the groupware option under Personal section. Currently on 21.0.4. Does this functionality require mail, contacts, calendars app installed and configured?

Thank you

It's a 23 feature. Please refrain from asking questions on a github pull request. This is not a forum. Use https://help.nextcloud.com/c/support/7 for questions ✌️