feat: Allow shared calendars as appointment conflict calendars

[SebastianKrupinski]

Resolves: nextcloud/calendar#3786
Requires: nextcloud/calendar#6411

Summary

Adjusted logic to use getCalendarsForUser to retrieve calendars, as this returns all personal and shared calendars.

[tcitworld]

This looks not very efficient? Since you're always fetching all of the user's calendars even if you want to get a single one?

Maybe something like this old PR instead ? #36681

[ChristophWurst]

@SebastianKrupinski what do you think about Thomas' suggestion? Is it doable?

[SebastianKrupinski]

@ChristophWurst I did have a look at the old PR. It can not be applied/used for this situation directly as the CalendarProvider uses the back end directly and not through the CalendarHome class, we could add the getSharedCalendarByUri method to the back end and then do a separate call in the CalendarProvider for any shared calendars.

As the CalendarProvider->getCalendars() takes in a array of uri's I though it would be more efficient to just make two calls to the database (all shared and all personal) and then filter out the required calendars instead of making two calls to the database for each uri (one for shared and one for personal). If the getCalendars() is called with 4 uris, one way we only make 2 database quires the other way we make 8.

What do you prefer?

[tcitworld]

Ah yes, it's a different case than #36681. You're right.

[ChristophWurst]

I'm not opposed this change but it has to be tested carefully.

Listing all calendars, also those which are shared by others, influences all places that use the \OCP\Calendar\IManager::getCalendarsForPrincipal public API. We can't easily build an exhaustive list of users because this API is also used by apps.

Some places that use it:

• dav app - user status automation. Events in shared calendars will make you show as In a meeting. Intended?
• dav app - TimezoneService. If a shared calendar with timezone information is listed before a owned calendar, it will influence the detected timezone of the user. Intended?
• polls app

[SebastianKrupinski]

I'm not opposed this change but it has to be tested carefully.

Listing all calendars, also those which are shared by others, influences all places that use the \OCP\Calendar\IManager::getCalendarsForPrincipal public API. We can't easily build an exhaustive list of users because this API is also used by apps.

Some places that use it:

* dav app - user status automation. Events in shared calendars will make you show as _In a meeting_. Intended?

* dav app - TimezoneService. If a shared calendar with timezone information is listed before a owned calendar, it will influence the detected timezone of the user. Intended?

* polls app

As per our conversation, the returns are logically the same. The previous code path would return all calendars if no uri's are provided and only the asked for calendars if uri's are provided. The only real change is where the calendars list is sourced and how its filtered.

[ChristophWurst]

Code looks good! Did not test