[FEATURE] Modify Additional Guests behavior on Registration page

[ppetersen15]

Have you shared this feature idea request in the Trailblazer Community?
Yes. https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007cleW8SAI

Is your feature request related to a problem? Please describe.
Kind of. When you configure a Summit Event record to allow for Other Attendees with a Max Other Attendee value, the registration page will feature a picklist field with values from 0 to the Max Other Attendee value, incremented by 1. If Current Available Capacity >1, the registration page will allow any selection, ignoring the current available capacity. If a registrant selects a value higher than the current available capacity on the instance, it will process the registration without error, and display a negative Current Available Capacity value on the record. Only after that registration is processed will the instance close due to capacity.

Describe the solution you'd like
Allow Other Attendees checkbox and Max Other Attendees number field on Summit Events record, as well as the Capacity field on the Summit Events Instance remain the same. On the registration page, the Additional Guests field will display a picklist with values from 0 to up to MINIMUM[ Available Capacity minus 1 OR Max Other Attendees value], incrementing by 1.

Describe alternatives you've considered
There's not a lot of other alternatives. Right now we are looking at reports for negative capacity and providing them to our users for follow-up with the registrants.

Are you willing and interested in being engaged during the development and testing process?
Yes