r/postgresql-cert: ACME certificates using certbot

This role can be used to get a server certificate for PostgreSQL from an
ACME CA using `certbot`.  It fetches the initial certificate and copies
it to the PostgreSQL configuration directory.  It also sets up a
post-renewal hook script that copies updated certificates and reload
the server.

roles/postgresql-cert/handlers/main.yml

@@ -0,0 +1,8 @@
+- name: reload systemd
+  systemd:
+    daemon_reload: true
+
+- name: restart certbot-renew timer
+  systemd:
+    name: certbot-renew.timer
+    state: restarted