Fix relays UI being available in whitelist/secure mode (#11963)

Fix relays UI referencing relay that is not functional

app/controllers/admin/relays_controller.rb

@@ -3,6 +3,7 @@
 module Admin
   class RelaysController < BaseController
     before_action :set_relay, except: [:index, :new, :create]
+    before_action :require_signatures_enabled!, only: [:new, :create, :enable]
 
     def index
       authorize :relay, :update?
@@ -11,7 +12,7 @@ module Admin
 
     def new
       authorize :relay, :update?
-      @relay = Relay.new(inbox_url: Relay::PRESET_RELAY)
+      @relay = Relay.new
     end
 
     def create
@@ -54,5 +55,9 @@ module Admin
     def resource_params
       params.require(:relay).permit(:inbox_url)
     end
+
+    def require_signatures_enabled!
+      redirect_to admin_relays_path, alert: I18n.t('admin.relays.signatures_not_enabled') if authorized_fetch_mode?
+    end
   end
 end

app/models/relay.rb

@@ -12,8 +12,6 @@
 #
 
 class Relay < ApplicationRecord
-  PRESET_RELAY = 'https://relay.joinmastodon.org/inbox'
-
   validates :inbox_url, presence: true, uniqueness: true, url: true, if: :will_save_change_to_inbox_url?
 
   enum state: [:idle, :pending, :accepted, :rejected]
@@ -74,7 +72,6 @@ class Relay < ApplicationRecord
   end
 
   def ensure_disabled
-    return unless enabled?
-    disable!
+    disable! if enabled?
   end
 end