The models in this folder represent VIEWS in the DB. Since the VIEWS
 are created separately, the model classes are "unmanaged". Unmanaged
 models do not trigger migrations that change the schema. However,
 a change to any of these model classes will trigger a migration, but
 the migration does to change the schema.

 Each model class has a corresponding SQL file. A migration has been
 created to run the ``CREATE VIEW`` commands using the
 ``migrations.RunSQL`` method.

 If you change the ``CREATE VIEW`` command, you have to generate a
 new empty migration which calls ``migrations.RunSQL`` to re-run the
 modified ``CREATE VIEW`` SQL command.
 (remember to ``DROP VIEW`` first.)
