services: use subdomain for ACME cert

Avoids conflicts now that I have multiple servers sharing the config

services/jellyfin.nix

@@ -14,6 +14,8 @@
   my = config.my;
 
   domain = config.networking.domain;
+  hostname = config.networking.hostName;
+  fqdn = "${hostname}.${domain}";
 
   # hardcoded in NixOS module :(
   jellyfinPort = 8096;
@@ -31,12 +33,14 @@ in {
     # Proxy to Jellyfin
     services.nginx.virtualHosts."jellyfin.${domain}" = {
       forceSSL = true;
-      useACMEHost = domain;
+      useACMEHost = fqdn;
 
       locations."/" = {
         proxyPass = "http://localhost:${toString jellyfinPort}/";
         proxyWebsockets = true;
       };
     };
+
+    security.acme.certs.${fqdn}.extraDomainNames = ["jellyfin.${domain}"];
   };
 }