add exam authors to collection/exam base

generic/mixins.py

@@ -29,3 +29,11 @@ class AuthorMixin():
         if not authors:
             return "None"
         return authors
+
+    def add_author(self, user: User):
+        """Add an author to the object"""
+        self.author.add(user)
+
+    def remove_author(self, user: User):
+        """Remove an author from the object"""
+        self.author.remove(user)

generic/models.py

@@ -572,6 +572,11 @@ class ExamOrCollectionGenericBase(models.Model, AuthorMixin):
         default=True,
     )
 
+    authors_only = models.BooleanField(
+        help_text="If true only exam/collection authors will be able to view.",
+        default=False,
+    )
+
     class Meta:
         abstract = True
 
@@ -803,11 +808,6 @@ class ExamBase(ExamOrCollectionGenericBase):
         default=1, help_text="auto incrementing field when json recreated"
     )
 
-    authors_only = models.BooleanField(
-        help_text="If true only exam authors will be able to view.",
-        default=False,
-    )
-
     stats_mean = models.FloatField(default=0)
     stats_mode = models.CharField(default=0, max_length=25)
     stats_median = models.FloatField(default=0)