Seems like this should be "easy" or at least documented somewhere, I just cant find it.

Lets say I have a model:

class A(models.Model):
    users = models.ManyToMany('auth.User', blank=True)

Now I want to migrate to have a through table to add fields to the ManyToMany relation...

class AUsers(models.Model):
    user = models.ForeignKey('auth.User')
    a = models.ForeignKey('A')
    new_field = models.BooleanField()

class A(models.Model):
    users = models.ManyToMany('auth.User', blank=True, through='AUsers')

Then I do:

% ./manage.py schemamigration app --auto

Not totally surprising, it tells me it is going to drop the original auto-created through table and create a new one for AUsers. What's the best practice at this point? Is there a decent way to migrate to the new through table? Do I use db_table in Meta? Do I just not use the through=... right away... then do a schemamigration --auto, then a datamigration to copy the current table (somehow, not sure...) and then add the through relation and let it kill the table?

What's the trick here? Is this really that hard?

django django-south
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