roles/postgresql-server: Support SSL configuration

This commit adds a task to generate a PostgreSQL configuration file from
a template.  Previously, the default configuration file generated by
`initdb` was sufficient, but in order to enable SSL connections, some
changes to it are required.

Naturally, SSL connections require a server certificate, so the
*postgresql-server* role will now also copy certificate files to the
managed node, if any.

roles/postgresql-server/handlers/main.yml

@@ -1,5 +1,9 @@
 - name: reload systemd
   command: systemctl daemon-reload
+- name: restart postgresql server
+  service:
+    name: postgresql
+    state: restarted
 - name: reload postgresql server
   service:
     name=postgresql