Enable users to select multiple slots or time range for appointments

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

As an event location, we'd want to use appointments to schedule external events in our rooms. These events range from 1h to a whole day. Currently the external groups can only select one slot and would have to repeat the progress for more time.

Describe the solution you'd like

We'd like a solution where one can either:

• select multiple slots in one booking (it would be sufficient if only consecutive times could be selected)
• select a time range (we could simulate this with the solution above and time slots of 1h)

Describe alternatives you've considered

The collision check doesn't work with other solutions

Additional context

No response

Start by tracing the existing appointment booking flow and its collision check. Compare the two requested interaction models—consecutive slot selection and direct time-range selection—and clarify how booking, validation, and conflicts should behave. Done means an external group can reserve multiple consecutive slots or a time range in one booking without collision-check regressions.