Because we have ATOMIC_REQUESTS turned on, the COURSE_CERT_CHANGED
signal was being sent *before* the date override was committed to the
database. This means that the date override data sent to credentials on
CertificateDateOverride save() was always one commit behind.
Django provides an on_commit() function to allow us to perform actions
only after a transaction is completed successfully. I believe this
is when we want this signal to be sent.
This is an alternative to 1) disabling atomic transactions for a view
(honestly, I’m not sure which view we would target anyway), or 2)
passing more data down through the signal.
Toward MICROBA-1423
eb2d606283