Although I haven't looked the original thread, it seems that the dbname is used only by pg_sync_replication_slots(). If it is true, couldn't we make the SQL function require a database name to make a connection, instead of requiring it in physical-replication conninfo?
In the original thread, the intention is to not just provide this functionality using the function pg_sync_replication_slots(), but provide a GUC option on standbys to sync logical replication slots periodically even without calling that function. This requires connecting to a database.
