Change about page to be mounted in the web UI (#19345)

app/controllers/api/v1/instances/domain_blocks_controller.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class Api::V1::Instances::DomainBlocksController < Api::BaseController
+  skip_before_action :require_authenticated_user!, unless: :whitelist_mode?
+
+  before_action :require_enabled_api!
+  before_action :set_domain_blocks
+
+  def index
+    expires_in 3.minutes, public: true
+    render json: @domain_blocks, each_serializer: REST::DomainBlockSerializer, with_comment: (Setting.show_domain_blocks_rationale == 'all' || (Setting.show_domain_blocks_rationale == 'users' && user_signed_in?))
+  end
+
+  private
+
+  def require_enabled_api!
+    head 404 unless Setting.show_domain_blocks == 'all' || (Setting.show_domain_blocks == 'users' && user_signed_in?)
+  end
+
+  def set_domain_blocks
+    @domain_blocks = DomainBlock.with_user_facing_limitations.by_severity
+  end
+end

app/controllers/api/v1/instances/extended_descriptions_controller.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class Api::V1::Instances::ExtendedDescriptionsController < Api::BaseController
+  skip_before_action :require_authenticated_user!, unless: :whitelist_mode?
+
+  before_action :set_extended_description
+
+  def show
+    expires_in 3.minutes, public: true
+    render json: @extended_description, serializer: REST::ExtendedDescriptionSerializer
+  end
+
+  private
+
+  def set_extended_description
+    @extended_description = ExtendedDescription.current
+  end
+end