Add language to iiif3 metadata writer

Fixes #1222

app/models/iiif3_metadata_writer.rb

@@ -13,8 +13,8 @@ def initialize(cocina_descriptive:, collection_title:, published_date:, doi:)
 
   # @return [Array<Hash>] the IIIF v3 metadata structure
   def write # rubocop:disable Metrics/AbcSize
-    available_online + titles + contributors + contacts + types + format + notes +
-      subjects + coverage + dates + identifiers + collection + publication
+    available_online + titles + contributors + contacts + types + format + language +
+      notes + subjects + coverage + dates + identifiers + collection + publication
   end
 
   private
@@ -79,6 +79,11 @@ def format
     vals.present? ? [iiif_key_value('Format', vals)] : []
   end
 
+  def language
+    vals = Array(cocina_descriptive['language']).map { it['value'] || it['code'] }
+    vals.present? ? [iiif_key_value('Language', vals)] : []
+  end
+
   def genre
     filtered_form('genre').map do
       it['value']

spec/integration/purl_spec.rb

@@ -27,7 +27,7 @@
           visit '/bc854fy5899/iiif3/manifest'
           json_body = JSON.parse(page.body)
           expect(json_body['label']['en'].first).to eq('John Wyclif and his followers, Tracts in Middle English')
-          expect(json_body['metadata'].length).to eq 11
+          expect(json_body['metadata'].length).to eq 12
         end
       end
 

spec/model/iiif3_metadata_writer_spec.rb

@@ -303,5 +303,17 @@
         end['value'][:en]).to eq ['51.5 x 59.8 cm., including title along top and border, with 10 diagrams/maps and 6 columns of titled text.']
       end
     end
+
+    context 'with language' do
+      let(:cocina_descriptive) do
+        PurlResource.find('zf119tw4418').version(:head).cocina['description']
+      end
+
+      it 'extracts the metadata' do
+        expect(metadata.find do
+          it['label'][:en] == ['Language']
+        end['value'][:en]).to eq ['eng']
+      end
+    end
   end
 end

spec/requests/iiif3_manifest_spec.rb

@@ -160,7 +160,7 @@
     get '/zf119tw4418/iiif3/manifest'
 
     expect(json['items'].length).to eq 58
-    expect(json['metadata'].length).to eq 12
+    expect(json['metadata'].length).to eq 13
   end
 
   context 'when pages do not have OCR content' do
@@ -363,7 +363,7 @@
       get "/#{druid}/iiif3/manifest"
       expect(response).to have_http_status(:ok)
       expect(json['label']['en'].first).to eq '10 Meter Contours: Russian River Basin, California'
-      expect(json['metadata'].size).to eq 11
+      expect(json['metadata'].size).to eq 12
     end
   end