How to implement user enrollment or subscription? I want to create a website with few courses in it. Each course will have a node of content type Course. I want users to be able to enter the course. 

So this is sort of a "many-to-many" relationship question for Drupal, as for each subscription I will need to keep details on the progress, e.g. "last completed lesson", "total score", etc.

Is there a module that will have Enrollment/Subscription as a separate Entity/Content or Relation module will do it?

What is the best approach?

UPDATE 1:


This should allow to show all students subscribed to a course on a course page;
Show all current subscriptions with their details (fields) to student on my_courses page. 


UPDATE 2: Can I use Open Group module for that?
It seems that this can be done with Entity Registration module.