Ad-hoc multiple capacity

[nickevansuk]

It is currently possible to configure Flow so that ad-hoc facilities bookings can be used for high frequency sessions in some specific cases. This primarily impacts "Gym and Swim".

For example, if a high frequency Swim session (e.g. "Swim for Fitness 25M") needs to be scheduled with overlapping start times, it is currently treated as a facility that can be booked multiple times in Flow.

This results in the following:

{
  "@type": "Slot",
  ....
  "maximumUses": 8,
  "remainingUses": 8
}

The maximumUses must always be 1 for an IndividualFacilityUse Slot, as a Slot is designed to represent e.g. "Court 1" of a facility. Court 1 can only be booked once, as it is a facility. If users can book "Court 1" more than once, that is described as a session from an OpenActive perspective (and therefore references the activity list - e..g "Swimming" - rather than the facility type list), and is described and expected to be displayed as such.

Options for resolution appear to be:

1. Flow is updated so that adhocs must be bookable only once, and sessions within Flow are updated to allow overlapping scheduling.
2. Flow is updated so that adhocs bookable more than once are included in the sessions feed (as high-frequency sessions) instead of the facility uses feed, and also updated so that such adhocs can be assigned SessionSeries metadata rather than FacilityUse metadata
3. The Option 3 from Proposal #301 is taken forward within OpenActive, and Flow is updated so that all high-frequency sessions (whether sessions or ad-hocs) are outputted in an additional pair of feeds.