Reservation Group Creation Issue

We have successfully rolled back the change and confirmed that reservation groups are now being created correctly. A page reload is required to apply the changes.

Note: Reservations created during the incident may still be in separate reservation groups instead of the intended shared group. Please review reservations created between 10:55 UTC and 14:23 UTC for any regrouping needs.

We've identified an issue affecting how reservation groups are created:
- Availability blocks using "All in one group" pickup distribution are currently failing with a validation error
- For all other reservation types, new reservation groups are being created incorrectly instead of adding reservations to existing groups when appropriate

We've identified the root cause and are currently rolling back the change that introduced this issue.