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

app/lib/admin/metrics/dimension.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class Admin::Metrics::Dimension
+  DIMENSIONS = {
+    languages: Admin::Metrics::Dimension::LanguagesDimension,
+    sources: Admin::Metrics::Dimension::SourcesDimension,
+    servers: Admin::Metrics::Dimension::ServersDimension,
+    space_usage: Admin::Metrics::Dimension::SpaceUsageDimension,
+    software_versions: Admin::Metrics::Dimension::SoftwareVersionsDimension,
+  }.freeze
+
+  def self.retrieve(dimension_keys, start_at, end_at, limit)
+    Array(dimension_keys).map { |key| DIMENSIONS[key.to_sym]&.new(start_at, end_at, limit) }.compact
+  end
+end