Add admin UI for managing email subscriptions (#38741)

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/controllers/admin/email_subscriptions/setups_controller.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+class Admin::EmailSubscriptions::SetupsController < Admin::BaseController
+  before_action :require_enabled!
+
+  def show
+    authorize :email_subscription, :enable?
+
+    @form = Form::EmailSubscriptionsConfirmation.new
+  end
+
+  def create
+    authorize :email_subscription, :enable?
+
+    @form = Form::EmailSubscriptionsConfirmation.new(resource_params)
+
+    if @form.valid?
+      Setting.email_subscriptions = true
+      redirect_to admin_email_subscriptions_path
+    else
+      render :show
+    end
+  end
+
+  private
+
+  def require_enabled!
+    raise ActionController::RoutingError, 'Feature disabled' unless Rails.application.config.x.email_subscriptions
+  end
+
+  def resource_params
+    params.expect(form_email_subscriptions_confirmation: [:agreement_email_volume, :agreement_privacy_and_terms])
+  end
+end