Unofficial participants and option to remove them from ranking

[stefano-maggiolo]

This means:

• sadly add another boolean field in the participation table to mark contestants as unofficial
• send this info to RWS
• add a checkbox to the scoreboard that controls whether they are visible or not (if there is at least one unofficial participant).

[lw]

A couple of remarks.

• Maybe this could be merged with hidden, for example by replacing it with a field ranking_status, defined as an enum taking values "visible", "unofficial", "hidden". Not sure whether hidden has other side-effects, though...
• Also, we need to decide how to rank unofficial contestants: do we want the ranks to be calculated for all contestants that are currently visible (meaning that, when the unofficial ones are shown, they are ranked as if they were to receive medals) or do we want the unofficial contestants to have an undefined ranking? The former option is IMO quite hard to implement (not in general, but with the current architecture of RWS) and also less desirable feature-wise. I'm strongly in favor of the latter.

[wil93]

I think the proposal to change hidden into raking_status is a good idea because there may be different degrees of being unofficial, e.g. at IOI there is the unofficial team, but there could also be online participants, and it may be nice to mark them in some way.