docker: add delayed job worker to compose file.

bin/wait-for-http

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+# Script to wait until an http service is ready. Used by the Docker Compose
+# file to wait until services are ready.
+#
+# Usage: bin/wait-for-http 3s http://google.com && echo ready
+
+set -euo pipefail
+
+URL="$1"
+DELAY="${2:-3s}"
+
+until curl -sL "$URL" > /dev/null; do
+  echo "$URL not up yet; retrying in $DELAY"
+  sleep "$DELAY"
+done