Add global setting for own nostr relay

app/views/admin/settings/services/_nostr.html.erb

@@ -19,6 +19,11 @@
         title: "Public key",
         description: "The corresponding public key of the accounts service"
       ) %>
+  <%= render FormElements::FieldsetResettableSettingComponent.new(
+        key: :nostr_relay_url,
+        title: "Relay URL",
+        description: "Websockets URL of a relay associated with #{Setting.primary_domain}"
+      ) %>
 </ul>
 </section>
 <section>