[feature] Add NC workflow to move finalized appointments between calendars

[nolens]

Initial issue was:
When adding appointment slots manually, they are not showing on public page

Steps to reprocude:

1. Add time slot manually in existing calendar

2. Set time to floating, category to "Appointment", status to "Tentative", the appointment is not showing on public page.

[SergeyMosin]

It should still work, but at this point it is discouraged. I have updated the "Help/Tutorial" section. The "Schedule Generator" has been updated and it is possible now to add a single appointments to virtually any time slot, or you can just move appointments around in the calendar interface.
However when there is progress on nextcloud/calendar#812 I was thinking of adding "Convert to Appointment" option to this calendar menu:

[nolens]

Or better even: Provide the possibility to add a "nextcloud workflow" so that once an appointment is finalized, it will be moved or copied automatically from "Appointment slot calendar A" to "Calendar B" (can be defined freely via workflow).

How does that sound?

[nolens]

Similar option added in version 1.5

Great and thank you, @SergeyMosin !