Include photographers as "priority/role" question when signing up for event

[Cajsshops]

Since photographers are multiple people that don't always work, we need the people that are photographers to be able to say that they are going to work that sitting/event in sign-up and then they are guaranteed a place at the event. This choice only shows up for people who actually have the post "photographer" to make sure noone just does it to always go to events

[Cajsshops]

this applies to the DJ role as well