Make default user services configurable by admin

spec/models/setting_spec.rb

@@ -8,14 +8,16 @@ RSpec.describe Setting, type: :model do
       Setting.ejabberd_enabled = true
       Setting.email_enabled = false
       Setting.gitea_enabled = false
+      Setting.lndhub_enabled = true
       Setting.mastodon_enabled = true
       Setting.mediawiki_enabled = false
+      Setting.nostr_enabled = false
       Setting.remotestorage_enabled = true
     end
 
     it "contains all enabled services" do
       expect(Setting.available_services).to eq(%w[
-        discourse ejabberd mastodon remotestorage
+        discourse ejabberd lndhub mastodon remotestorage
       ])
     end
   end