implement user database deletion

- modify userdbs.models.UserDatabase.delete to perform deletion of database
  user if it has no other databases assigned
- implement userdbs.views.DeleteUserDatabase
- add URL pattern 'delete_userdatabase' to userdbs.urls
- add template userdbs/userdatabase_confirm_delete.html
- add link to 'delete_userdatabase' on hosting package detail page
- add changelog entry

gnuviechadmin/userdbs/models.py

@@ -287,10 +287,13 @@ class UserDatabase(TimeStampedModel, models.Model):
             :py:meth:`django.db.models.Model.delete`
 
         """
-        if self.db_user.db_type == DB_TYPES.pgsql:
+        db_user = self.db_user
+        if db_user.db_type == DB_TYPES.pgsql:
             delete_pgsql_database.delay(self.db_name).get()
-        elif self.db_user.db_type == DB_TYPES.mysql:
-            delete_mysql_database.delay(self.db_name, self.db_user.name).get()
+        elif db_user.db_type == DB_TYPES.mysql:
+            delete_mysql_database.delay(self.db_name, db_user.name).get()
         else:
             raise ValueError('Unknown database type %d' % self.db_type)
         super(UserDatabase, self).delete(*args, **kwargs)
+        if not db_user.userdatabase_set.exists():
+            db_user.delete()