Allow Mastodon address domain to be different from primary domain

app/models/setting.rb

@@ -106,6 +106,9 @@ class Setting < RailsSettings::Base
   field :mastodon_enabled, type: :boolean,
     default: (ENV["MASTODON_PUBLIC_URL"].present?.to_s || false)
 
+  field :mastodon_address_domain, type: :string,
+    default: ENV["MASTODON_ADDRESS_DOMAIN"].presence || self.primary_domain
+
   #
   # MediaWiki
   #

app/models/user.rb

@@ -110,6 +110,11 @@ class User < ApplicationRecord
     "#{self.cn}@#{self.ou}"
   end
 
+  def mastodon_address
+    return nil unless Setting.mastodon_enabled?
+    "#{self.cn}@#{Setting.mastodon_address_domain}"
+  end
+
   def valid_attribute?(attribute_name)
     self.valid?
     self.errors[attribute_name].blank?

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

@@ -12,5 +12,9 @@
           key: :mastodon_public_url,
           title: "Public URL"
         ) %>
+    <%= render FormElements::FieldsetResettableSettingComponent.new(
+          key: :mastodon_address_domain,
+          title: "User address domain"
+        ) %>
   <% end %>
 </ul>

app/views/services/mastodon/show.html.erb

@@ -13,7 +13,7 @@
     </p>
     <p data-controller="clipboard" class="flex gap-1 sm:w-2/5">
       <input type="text" id="user_address" class="grow"
-             value=<%= current_user.address %> disabled="disabled"
+             value=<%= current_user.mastodon_address %> disabled="disabled"
              data-clipboard-target="source" />
       <button id="copy-user-address" class="btn-md btn-icon btn-outline shrink-0"
               data-clipboard-target="trigger" data-action="clipboard#copy"