Allow organisers to refund tickets more freely

[timiwahalahti]

Sometimes, organisers need to refund tickets on behalf of the attendee when the refunds are turned off. Sometimes, they also need to refund free tickets, for example, when a volunteer cancels their attendance.

In this PR:

• Refund link is added to singular attendee edit view, with an indication if that will work for attendee or only for organisers
• Users with manage_attendees capability can do refunds even if refunds are turned off
• Users with manage_attendees capability can refund free tickets

Fixes #761
Fixes #770

Props @iandunn

Screenshots

Refund link on attendee edit, when refunds are turned off.

Refund link on attendee edit information table, when refunds are turned on.

How to test the changes in this Pull Request:

1. Open WordCamp site, create ticket and 100% discount code
2. Purchase tickets by paying and with discount code
3. Check that refunds are off
4. Open one of the attendees and their refund request links, you should be able to see the refund form
5. Do the same but open links on incognito, refund form should not be visible
6. Try to refund attendee which was purchased with discount code

[renintw]

Need @WordPress/community-admins feedback on this PR.
Does the updated workflow make sense?
Is there anything that can be done better or are there alternative solutions in terms of refund issues mentioned?

[ciudadanoB]

Hi @renintw!

I think it's still needed, yes. It's probably not used widely in small WordCamps or events, but it happens a lot in flagship events. We have people who apply as volunteers and then, weeks after, announce they're not able to come to the event, so we need to cancel their free tickets.

Currently, it's only possible to do so by the program managers or the meta team, so the organisers need to send a list of free tickets to be cancelled or refunded so they can export the data later with the current list of people attending the event.

If site admins could do it by themselves, it would be great!