Make appointment reasons default to a set duration (e.g. H30 = 30 minutes)

At the moment, appointment reasons don’t have a default duration, so H30 always needs the duration selecting at the time you book. This is inefficient when H30 should always be 30 minutes for all practitioners. Please add a setting so an appointment reason can be configured to default to a specific duration (e.g. 30 minutes), rather than having to pick it each time.