Give proper support for different types of assignment codes

[DanielEgdal]

On the competitor's own overview page, all types of possible assignments are written https://www.competitiongroups.com/competitions/RoskildeForAlle2022/persons/1

However, it lacks two kinds of (somewhat easy) supports.
1: For assignment codes, if there is a 'staff-' prefix, this should not be displayed. If the assignment code is listed as 'staff-runningJudge' it would be displayed as exactly that, where it would make sense to simply write 'runningJudge'.

2: On the activity overview (https://www.competitiongroups.com/competitions/RoskildeForAlle2022/activities/20), the other types of assignment codes are not listed. It should be as simple as making the same kind of header as for all the other assignments and list the people under it.

[coder13]

Keeping open because this isn't addressed on the events page however I want to re-do it at some point.