current agc_exposure table does not match defined constraints.

I've bumped into this a few time running alembic on the current summit opdb.
So basically, models.py declare there is a contraint between pfs_visit.pfs_visit_id and agc_exposure_visit_id.

So, that you cannot insert on a pfs_visit_id that does not exist.
This is the right thing to do but, but right now, on the current instance, there is no constraint, so agc_visit.pfs_visit_id can take whatever value, erk...

I cannot easily add the contraint because there is pfs_visit_id in agc_exposure which does not exist in pfs_visit table :

set(agc[:,1]) - set(pfs[:,0])
   {0, 99999, 779594}

From what I understand, cloomis, agc_exposure does not necessarily have a valid pfs_visit, so it's set to 0 in that case, which is fine and we could add that "fake" pfs_visit_id into pfs_visit to respect the constraint. but 99999, 779594 are valid pfs_visit_id and those will eventually exist causing troubles.

Fixing the issue boils down to basically 3 things to do :

1. setting pfs_visit_id to 0 where pfs_visit_id==99999 or 779594
2. adding a row in pfs_visit where pfs_visit_id=0
3. adding the contraint between agc_exposure.pfs_visit_id and pfs_visit.pfs_visit_id