chore: wait for postgres in docker compose

docker/wait-for-postgres.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+set -e
+
+until psql -h "$POSTGRES_HOST" -U "$POSTGRES_USERNAME" -d "$POSTGRES_HOST" -c '\q'; do
+  >&2 echo "Postgres is unavailable - sleeping"
+  sleep 1
+done
+
+>&2 echo "Postgres is up - executing command"
+exec "$@"