fix: Use -P pager=off in the psql commands. (#631)

This allows for non-interactive use and doesn't hang on the user
input in certain conditions, like when the command output is large.

Fixes #610

core/docker-entrypoint.sh

@@ -6,7 +6,7 @@ function wait_for_postgres () {
 	# moving forward.
 	# TODO: Use python3's psycopg2 module to do this in python3 instead of
 	# installing postgres-client in the image.
-	until psql $DATABASE_URL -c '\l'; do
+	until psql -P pager=off $DATABASE_URL -c '\l'; do
 		>&2 echo "Postgres is unavailable - sleeping"
 		sleep 1
 	done