Add graphs and retention metrics to admin dashboard (#16829)

app/lib/admin/metrics/measure.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class Admin::Metrics::Measure
+  MEASURES = {
+    active_users: Admin::Metrics::Measure::ActiveUsersMeasure,
+    new_users: Admin::Metrics::Measure::NewUsersMeasure,
+    interactions: Admin::Metrics::Measure::InteractionsMeasure,
+    opened_reports: Admin::Metrics::Measure::OpenedReportsMeasure,
+    resolved_reports: Admin::Metrics::Measure::ResolvedReportsMeasure,
+  }.freeze
+
+  def self.retrieve(measure_keys, start_at, end_at)
+    Array(measure_keys).map { |key| MEASURES[key.to_sym]&.new(start_at, end_at) }.compact
+  end
+end