Is your feature request related to a problem? Please describe

It is currently not possible to link an event to an existing room booking during the cloning process. This is rather confusing for event managers, as the only way for them to link the newly cloned event to a room booking is via creating a new room booking from the event management interface (event/1/manage/rooms/).

Describe the solution you'd like

The solution I propose is to have a 5th step in the event cloning dialog, where the event manager can select an existing room booking to link the cloned event to. In principle, the only bookings that the event manager is able to select should be limited to those assigned to them and that are compatible with the chosen dates of the cloned event. This option should only be available for "Clone Once".

Describe alternatives you've considered

An alternative to doing this in the event cloning dialog would be to add a way in the event management interface (event/1/manage/rooms/) that allows the event manager to link the event to an existing room booking. This would be perhaps a more general solution that the event cloning dialog could reuse.

Additional context

From my brief chat with @ThiefMaster via Matrix about this, one limitation is that events can only be linked to room bookings and not to booking occurrences. This means that linking an event to a booking with many occurrences will prevent the booking to be linked to a different event. Should it, then, be possible to link events to single-occurrence bookings only for now?