[Camptix] show attendee only once in case of multiple registrations

[ethicaladitya]

This is an improvement feature for the Camptix attendee page.

In case, somebody is purchasing tickets for their team, they might be using their own email initially. As a result, their Names/photo will be available on the attendees' page for the number of times they purchased tickets.

The proposal is to display the name/photo only once if multiple tickets are purchased and selected the option to "show on the attendee page".

Example: https://prnt.sc/70A85bSgMWer

[ryelle]

The idea to hide duplicate people has been suggested before, at #623. Closing this as a duplicate.