Django warnings about use of ForeignKey(unique=True)

[ssciolla]

When starting up the project via docker-compose, there are a number of messages from Django suggesting that we should consider replacing the use of ForeignKey(unique=True) for model fields with OneToOneField. The messages specifically look like this:

seumich.ClassSiteScore.class_site: (fields.W342) Setting unique=True on a ForeignKey has the same effect as using a OneToOneField.
HINT: ForeignKey(unique=True) is usually better served by a OneToOneField.

If we have the bandwidth at some point, it would be nice to make these changes, so we're following best practice and (more importantly, for our daily lives) we don't see these messages any more.