Out-of-office: Apply user info to auto responder settings (if enabled)

[st3iny]

Is your feature request related to a problem? Please describe.

There will be a global absence form in the personal settings. Those settings should be integrated with our autoresponder.

Tracked in nextcloud/server#40397

Probably requires nextcloud/server#40650 to fetch the actual data

Describe the solution you'd like

Global out-of-office data should be applied to the autoresponder form.

Describe alternatives you've considered

None

Additional context

No response

[ChristophWurst]

Idea for the Mail settings: make the switch ternary:

1. Auto responder off
2. Auto responder enabled
3. Auto responder follows system setting

Default should be on off, I think.

For provisioning we have an option to enable Sieve. There could be a checkbox to enable system autoresponders by default.