Implement easy sliding sync setup

Co-authored-by: h7x4 <h7x4@nani.wtf>

sliding-sync/default.nix

@@ -15,6 +15,13 @@ in
       description = "What package to use for the sliding-sync proxy.";
     };
 
+    enableNginx = lib.mkEnableOption (lib.mdDoc "autogenerated nginx config");
+    publicBaseUrl = lib.mkOption {
+      type = lib.types.str;
+      description = "The domain where clients connect, only has an effect with enableNginx";
+      example = "slidingsync.matrix.org";
+    };
+
     settings = lib.mkOption {
       type = lib.types.submodule {
         freeformType = with lib.types; attrsOf str;
@@ -98,5 +105,13 @@ in
         WorkingDirectory = "%S/matrix-sliding-sync";
       };
     };
+
+    services.nginx.virtualHosts.${cfg.publicBaseUrl} = lib.mkIf cfg.enableNginx {
+      enableACME = true;
+      forceSSL = true;
+      locations."/" = {
+        proxyPass = lib.replaceStrings [ "0.0.0.0" "::" ] [ "127.0.0.1" "::1" ] "http://${cfg.settings.SYNCV3_BINDADDR}";
+      };
+    };
   };
 }