Here's my problem.
I have a WordPress installation that has about 30 users with duplicates of emails in the users table. That's ok, because that's how I had to do it for the time being. I wanted users to register with exactly the same email because parents had to register their children into the system and their children did not have any email addresses (could be children from age 4 and up).
An example of the database could look like
email@example.com (parent) firstname.lastname@example.org (where this is child1 to parent) email@example.com (where this is child2 to parent)
I solved this temporarily (because I had to get this fixed quickly), but now I would like the users be able to login and change some stuff in their profile. Usernames and passwords are created and are totally unique so it's possible to login - but no one has received usernames or passwords because the initial thought was not to give them ability to login.
I could solve the issue by sending usernames and passwords to the user (parent and the parent's children) to
firstname.lastname@example.org and go through all the 30 users (parents) and do the same.
But my issue lays in how to handle future registrations. Each user must be unique cause each user has some custom fields related to itself.
It's about registrering different dance-courses. The dance academy wants to keep track of how many pupils (users) there are at any course and wants to keep to track of user has payed the course or not. Sometime the user can be set as reserve and sometimes not. To complicate it further it's not always this relationship between parent/child. Sometimes- let's say an 18-year old wants to register at 3 dance-courses and the user is "child" (or could at least handle the registration him/herself)