Truncate content above Discovery Engine limit

The current limit for Discovery Engine is 1MB of content, so truncate
the handful of obscenely large documents to 950KB.

app/models/concerns/publishing_api/content.rb

@@ -14,6 +14,7 @@ module Content
       $.details.more_information
     ].map { JsonPath.new(_1, use_symbols: true) }.freeze
     INDEXABLE_CONTENT_SEPARATOR = "\n".freeze
+    INDEXABLE_CONTENT_MAX_BYTE_SIZE = 950.kilobytes
 
     # Extracts a single string of indexable unstructured content from the document.
     def content
@@ -24,10 +25,14 @@ def content
         ["<h1>#{_1[:title]}</h1>", ContentWithMultipleTypes.new(_1[:body]).html_content]
       end
 
-      [
-        *values_from_json_paths,
-        *values_from_parts,
-      ].flatten.join(INDEXABLE_CONTENT_SEPARATOR)
+      [*values_from_json_paths, *values_from_parts]
+        .flatten
+        .join(INDEXABLE_CONTENT_SEPARATOR)
+        # Only take the first INDEXABLE_CONTENT_MAX_BYTE_SIZE bytes of the string
+        .byteslice(0, INDEXABLE_CONTENT_MAX_BYTE_SIZE)
+        # Remove any trailing invalid UTF-8 characters that might have been introduced through
+        # slicing the string
+        .scrub("")
     end
   end
 end

spec/models/concerns/publishing_api/content_spec.rb

@@ -72,6 +72,20 @@
       it { is_expected.to eq("<h1>Foo</h1>\nbar\n<h1>Bar</h1>\n<blink>baz</blink>") }
     end
 
+    describe "with excessively large content" do
+      let(:document_hash) do
+        {
+          details: {
+            body: "a" * 1.1.megabytes,
+          },
+        }
+      end
+
+      it "truncates the content" do
+        expect(extracted_content.bytesize).to be <= 1.megabyte
+      end
+    end
+
     describe "without any fields" do
       let(:document_hash) do
         {