refactoring: split helper functions into smaller scripts (#2420)

target/scripts/wrapper/postfix-wrapper.sh

@@ -0,0 +1,29 @@
+#! /bin/bash
+
+# You cannot start postfix in some foreground mode and
+# it's more or less important that docker doesn't kill
+# postfix and its chilren if you stop the container.
+#
+# Use this script with supervisord and it will take
+# care about starting and stopping postfix correctly.
+#
+# supervisord config snippet for postfix-wrapper:
+#
+# [program:postfix]
+# process_name = postfix
+# command = /path/to/postfix-wrapper.sh
+# startsecs = 0
+# autorestart = false
+#
+
+trap "service postfix stop" SIGINT
+trap "service postfix stop" SIGTERM
+trap "service postfix reload" SIGHUP
+
+service postfix start
+
+# wait until postfix is dead (triggered by trap)
+while kill -0 "$(< /var/spool/postfix/pid/master.pid)"
+do
+  sleep 5
+done