Merge pull request #16666 from nextcloud/feature/calendar/delegation

apps/dav/appinfo/info.xml

apps/dav/appinfo/v1/caldav.php

apps/dav/appinfo/v1/carddav.php

apps/dav/composer/composer/autoload_classmap.php

apps/dav/composer/composer/autoload_static.php

apps/dav/lib/CalDAV/Calendar.php

apps/dav/lib/CalDAV/Proxy/Proxy.php

apps/dav/lib/CalDAV/Proxy/ProxyMapper.php

...v/lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php

...v/lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php

apps/dav/lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php

apps/dav/lib/Command/CreateCalendar.php

apps/dav/lib/Connector/Sabre/Principal.php

apps/dav/lib/Migration/Version1011Date20190806104428.php

apps/dav/lib/RootCollection.php

apps/dav/lib/Server.php

apps/dav/lib/Traits/PrincipalProxyTrait.php

apps/dav/tests/unit/CalDAV/AbstractCalDavBackend.php

apps/dav/tests/unit/CalDAV/CalendarTest.php

...t/CalDAV/ResourceBooking/AbstractPrincipalBackendTest.php