Use infinite restarts for xsnippet-api.service

systemd defaults are fairly strict (<= 5 restarts within 10s) before
it gives up on the service. And we would prefer the service to recover
automatically after transient failures even if takes longer than that.

E.g. yesterday, I found that xsnippet-api had been down after the last
machine reboot because it could not fetch the Auth0 key on start, but
the same thing could happen with database connection as well.

Author: malor

roles/xsnippet_api/templates/systemd.service.j2

@@ -2,6 +2,7 @@
 Description = XSnippet API
 After = network.target network-online.target
 Wants = network-online.target
+StartLimitIntervalSec = 0
 
 [Service]
 WorkingDirectory = {{ xsnippet_api_root }}
@@ -11,6 +12,7 @@ Group = {{ xsnippet_api_user }}
 ExecStartPre = {{ xsnippet_api_database_upgrade_bin }}
 ExecStart = {{ xsnippet_api_bin }}
 Restart = on-failure
+RestartSec = 30
 
 [Install]
 WantedBy = multi-user.target