Add a course_groups djangoapp with a CourseUserGroup model.

common/djangoapps/course_groups/models.py

@@ -0,0 +1,27 @@
+from django.contrib.auth.models import User
+from django.db import models
+
+class CourseUserGroup(models.Model):
+    """
+    This model represents groups of users in a course.  Groups may have different types,
+    which may be treated specially.  For example, a user can be in at most one cohort per
+    course, and cohorts are used to split up the forums by group.
+    """
+    class Meta:
+        unique_together = (('name', 'course_id'), )
+
+    name = models.CharField(max_length=255,
+                            help_text=("What is the name of this group?  "
+                                       "Must be unique within a course."))
+    users = models.ManyToManyField(User, db_index=True, related_name='course_groups',
+                                   help_text="Who is in this group?")
+
+    # Note: groups associated with particular runs of a course.  E.g. Fall 2012 and Spring
+    # 2013 versions of 6.00x will have separate groups.
+    course_id = models.CharField(max_length=255, db_index=True,
+                                 help_text="Which course is this group associated with?")
+
+    # For now, only have group type 'cohort', but adding a type field to support
+    # things like 'question_discussion', 'friends', 'off-line-class', etc
+    GROUP_TYPE_CHOICES = (('cohort', 'Cohort'),)
+    group_type = models.CharField(max_length=20, choices=GROUP_TYPE_CHOICES)

lms/envs/common.py

@@ -577,6 +577,7 @@ INSTALLED_APPS = (
     'open_ended_grading',
     'psychometrics',
     'licenses',
+    'course_groups',
 
     #For the wiki
     'wiki', # The new django-wiki from benjaoming