Add new MarkerTimelinePresenter class

app/presenters/marker_timeline_presenter.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class MarkerTimelinePresenter
+  include ActiveModel::Model
+
+  alias read_attribute_for_serialization send
+
+  attr_reader :markers
+
+  def initialize(markers)
+    @markers = markers
+  end
+
+  Marker::TIMELINES.each do |timeline|
+    define_method timeline.to_sym do
+      markers.find { |marker| marker.timeline == timeline }
+    end
+  end
+
+  def timeline_present?(value)
+    markers.map(&:timeline).include?(value)
+  end
+end