Shows summary of all attendees with a paid ticket, including
boarding_pass status.
Currently, regidesk allows staff with the requisite permission the
ability to view the checkin status of attendees, and email the user
their boarding pass email.
Included is a view for the user to retrieve their own QR code (in case
they got the plain-text version of the email, they can use this to
download an image to their phone for faster checkin)
