This is the mode they want to work with, but i could not test it because
they do not have it enabled in Redsys. For now, just add the status and
the code to handle the responses.
Now i store all responses, if they are for a valid payment, just in case
i fucked something up. I also needed it because an authorization hold
needs at least two responses: one to accept the hold, and another for
the settlement.
I have to basically do the reverse of signing the request to verify that
the notification comes from them. Lots of code just for that.
I return the changed status from the PL/pgSQL function because i will
need to email customers when a payment is completed, and i need to know
when.