Make "future" practice problems invisible #860
Description
Often we want to re-use quiz questions from previous semesters, and some instructors (me included sometimes) are tempted to hide all quiz and homework problems in ALeA (at least until our database is big enough that we have so many that they can be public).
To encourage publishing quiz/hw problems, a middle ground might be that we make all "future" problems - i.e. with objectives that have not been covered in the current course according to the gottos - inaccessible (from that course). This should certainly be an instructor-configurable feature.
I am aware that this is probably non-trivial and needs design: According to our "problems everywhere" strategy there are many situations where practice problems may occur. But I think that this might make ALeA more palatable to instructors, since it does not "force" them to come up wiht new quiz questions every time.
I am also aware that students can probably somehow get access to the "future" practice problems (e.g. through old courses or other courses that alreay covered the topics), but I think that will not be a big problem in practice.