Ensure duplicate links are retained in array/hash

When a document is part of an array/hash (such as Mainstream documents),
we were still calling `.uniq` after going through each item. This meant
that documents such as Answers, Guides etc weren’t getting the correct
metadata, as any duplicate links were getting thrown away.

To get around this, we call `.uniq` BEFORE calling `.flatten`. This
ensures that we retain the number of instances without double counting
for multipart content.

app/services/embedded_content_finder_service.rb

@@ -11,9 +11,9 @@ def fetch_linked_content_ids(details, locale)
   def find_content_references(value)
     case value
     when Array
-      value.map { |item| find_content_references(item) }.flatten.uniq
+      value.map { |item| find_content_references(item) }.uniq.flatten
     when Hash
-      value.map { |_, v| find_content_references(v) }.flatten.uniq
+      value.map { |_, v| find_content_references(v) }.uniq.flatten
     when String
       ContentBlockTools::ContentBlockReference.find_all_in_document(value)
     else

spec/services/embedded_content_finder_service_spec.rb

@@ -86,6 +86,44 @@
         expect(links).to eq([editions[0].content_id, editions[1].content_id])
       end
 
+      it "returns duplicates when there is more than one content reference in the field and #{field_name} is a multipart document" do
+        details = {
+          field_name => [
+            {
+              body: [
+                {
+                  content: "some string with a reference: {{embed:#{document_type}:#{editions[0].content_id}}} {{embed:#{document_type}:#{editions[0].content_id}}}",
+                  content_type: "text/html",
+                },
+                {
+                  content: "some string with a reference: {{embed:#{document_type}:#{editions[0].content_id}}} {{embed:#{document_type}:#{editions[0].content_id}}}",
+                  content_type: "text/govspeak",
+                },
+              ],
+              slug: "some-slug",
+              title: "Some title",
+            },
+            {
+              body: [
+                {
+                  content: "some string with another reference: {{embed:#{document_type}:#{editions[1].content_id}}} {{embed:#{document_type}:#{editions[1].content_id}}}",
+                  content_type: "text/html",
+                },
+                {
+                  content: "some string with another reference: {{embed:#{document_type}:#{editions[1].content_id}}} {{embed:#{document_type}:#{editions[1].content_id}}}",
+                  content_type: "text/govspeak",
+                },
+              ],
+              slug: "some-other-slug",
+              title: "Some other title",
+            },
+          ],
+        }
+        links = EmbeddedContentFinderService.new.fetch_linked_content_ids(details, Edition::DEFAULT_LOCALE)
+
+        expect(links).to eq([editions[0].content_id, editions[0].content_id, editions[1].content_id, editions[1].content_id])
+      end
+
       it "finds content references when the field is a hash" do
         details = { field_name => { title: "{{embed:#{document_type}:#{editions[0].content_id}}}", slug: "{{embed:#{document_type}:#{editions[1].content_id}}}", current: true } }
 
@@ -94,6 +132,14 @@
         expect(links).to eq([editions[0].content_id, editions[1].content_id])
       end
 
+      it "returns duplicates when there is more than one content reference in the field and the field is a hash" do
+        details = { field_name => { title: "{{embed:#{document_type}:#{editions[0].content_id}}} {{embed:#{document_type}:#{editions[0].content_id}}}", slug: "{{embed:#{document_type}:#{editions[1].content_id}}}", current: true } }
+
+        links = EmbeddedContentFinderService.new.fetch_linked_content_ids(details, Edition::DEFAULT_LOCALE)
+
+        expect(links).to eq([editions[0].content_id, editions[0].content_id, editions[1].content_id])
+      end
+
       it "errors when given a content ID that is still draft" do
         details = { field_name => "{{embed:#{document_type}:#{draft_edition.content_id}}}" }