The SQL statement for discovering the cdr table tries to access a column which
has been obsolteted for a long time and was removed in PostgreSQL 12 (see
upstream bug for full discussion).
Attached patch (to be dropped in files/) makes sure cdr_pgsql works with all
supported (and much more) versions of PostgreSQL. It should work with
net/asterisk13 as well (I'm not filing another, redundant PR for that).