store gatus database persistently in sqlite

nix/modules/monitoring/default.nix

@@ -59,6 +59,11 @@ in
       settings = {
         web.port = 4242;
 
+        storage = {
+          type = "sqlite";
+          path = "/srv/gatus/gatus.db";
+        };
+
         alerting.email = {
           from = "gatus@kun.is";
           host = "mail.smtp2go.com";
@@ -75,5 +80,12 @@ in
         };
       };
     };
+
+    system.activationScripts = lib.mkIf cfg.server.enable {
+      gatus = ''
+        mkdir -p /srv/gatus
+        chown gatus:gatus /srv/gatus
+      '';
+    };
   };
 }