Qualify "affiliation" field

[albertoleoncio]

We need to add a qualification of the "affiliation" field. For example, specified if the user is a "member", "staff" or "follower/observer" of that organization. The user should be able to add multiple options, in case the user has multiple "links".

capx-backend/users/models.py

Line 145 in c0665b9

affiliation = models.ManyToManyField(