Add support for reloading Synapse

docs/howto-server-delegation.md

@@ -135,4 +135,5 @@ matrix_synapse_tls_certificate_path: /some/path/inside/the/container/certificate
 matrix_synapse_tls_private_key_path: /some/path/inside/the/container/private.key
 ```
 
-Every once in a while (before the certificates expire), you'll need to completely restart Synapse (unless [Synapse becomes capable of reloading certificates without restarting - issue #1180](https://github.com/matrix-org/synapse/issues/1180)). Restarting Synapse can be done like this: `systemctl restart matrix-synapse`. Restarting causes some downtime.
+Make sure to reload Synapse once in a while (`systemctl reload matrix-synapse`), so that newer certificates can kick in.
+Reloading doesn't cause any downtime.

roles/matrix-synapse/templates/synapse/systemd/matrix-synapse.service.j2

@@ -51,6 +51,7 @@ ExecStart=/usr/bin/docker run --rm --name matrix-synapse \
 
 ExecStop=-/usr/bin/docker kill matrix-synapse
 ExecStop=-/usr/bin/docker rm matrix-synapse
+ExecReload=/usr/bin/docker exec matrix-synapse kill -HUP 1
 Restart=always
 RestartSec=30