Add metadata concern and tests

Commit audit trail:
- https://github.com/alphagov/government-frontend/blob/a938e4bee78b794e4e5303a1bde1dfd05e94b287/app/presenters/content_item/metadata.rb
- https://github.com/alphagov/government-frontend/blob/a938e4bee78b794e4e5303a1bde1dfd05e94b287/test/presenters/content_item/metadata_test.rb

app/models/concerns/metadata.rb

@@ -0,0 +1,25 @@
+module Metadata
+  extend ActiveSupport::Concern
+
+  def details_display_date
+    content_store_hash.dig("details", "display_date")
+  end
+
+  def pending_stats_announcement?
+    details_display_date.present? && Time.zone.parse(details_display_date).future?
+  end
+
+  def publisher_metadata
+    metadata = {
+      from:,
+      first_published: first_published_at,
+      last_updated: updated,
+    }
+
+    unless pending_stats_announcement?
+      metadata[:see_updates_link] = true
+    end
+
+    metadata
+  end
+end

spec/models/concerns/metadata_spec.rb

@@ -0,0 +1,63 @@
+class DummyContentItem
+  include Metadata
+  attr_accessor :content_item
+
+  def content_store_hash
+    @content_item
+  end
+
+  def initialize
+    @content_item = {
+      "details" => {
+        "display_date" => nil,
+      },
+    }
+  end
+end
+
+RSpec.describe Metadata, type: :model do
+  let(:item) { DummyContentItem.new }
+
+  describe "#details_display_date" do
+    it "returns the display date from the content store hash" do
+      item.content_item["details"]["display_date"] = "2023-10-01"
+      expect(item.details_display_date).to eq("2023-10-01")
+    end
+  end
+
+  describe "#pending_stats_announcement?" do
+    it "returns true if display date is in the future" do
+      item.content_item["details"]["display_date"] = (Time.zone.now + 1.day).iso8601
+      expect(item.pending_stats_announcement?).to be true
+    end
+  end
+
+  describe "#publisher_metadata" do
+    before do
+      allow(item).to receive(:from).and_return("from_value")
+      allow(item).to receive(:first_published_at).and_return("2023-01-01")
+      allow(item).to receive(:updated).and_return("2023-10-01")
+    end
+
+    it "includes see_updates_link if not a pending stats announcement" do
+      item.content_item["details"]["display_date"] = (Time.zone.now - 1.day).iso8601
+      expected_metadata = {
+        from: "from_value",
+        first_published: "2023-01-01",
+        last_updated: "2023-10-01",
+        see_updates_link: true,
+      }
+      expect(item.publisher_metadata).to eq(expected_metadata)
+    end
+
+    it "does not include see_updates_link if a pending stats announcement" do
+      item.content_item["details"]["display_date"] = (Time.zone.now + 1.day).iso8601
+      expected_metadata = {
+        from: "from_value",
+        first_published: "2023-01-01",
+        last_updated: "2023-10-01",
+      }
+      expect(item.publisher_metadata).to eq(expected_metadata)
+    end
+  end
+end