Allow password file name to be specified as a libpq connection parameter.
Formerly an alternate password file could only be selected via the
environment variable PGPASSFILE; now it can also be selected via a
new connection parameter "passfile", corresponding to the conventions
for most other connection parameters. There was some concern about
this creating a security weakness, but it was agreed that that argument
was pretty thin, and there are clear use-cases for handling password
files this way.
Julian Markwort, reviewed by Fabien Coelho, some adjustments by me
Discussion: https://postgr.es/m/
a4b4f4f1-7b58-a0e8-5268-
5f7db8e8ccaa@uni-muenster.de