Allow solution downloads for superusers

[hannesbraun]

This allows superusers to download solutions (e.g. to reproduce errors of the Praktomat). Otherwise, you'd need to add the trainer role to the superuser first in order to get access, which is mildly inconvenient.

[ifrh]

looks good to me.
But it could differ from requirements given by local DSB.
(Could be, that admin is not allowed to see student solutions.)

Perhaps using django permissions and not testing roll flags could simplify code in that place.
On the other hand nowhere in Praktomat code permissions has been used so far (cf. KITPraktomatTeam/Praktomat#241 )

[hannesbraun]

But it could differ from requirements given by local DSB.
(Could be, that admin is not allowed to see student solutions.)

I thought about that, too. But then, the status quo is that the superuser can already view all the content of a solution in the browser. So it he won't get access to data he wasn't able to access beforehand. Life is just getting easier. At least, that's my point of view ;)

Perhaps using django permissions and not testing roll flags could simplify code in that place.
On the other hand nowhere in Praktomat code permissions has been used so far (cf. KITPraktomatTeam/Praktomat#241 )

Maybe I can look into that at some point in the future... There are other places in the code base, where that might be useful as well. For now, I'd say it's fine.