use correct content disposition for local files

lib/api/helpers/attachment_renderer.rb

@@ -44,7 +44,7 @@ module API
           redirect attachment.external_url.to_s
         else
           content_type attachment.content_type
-          header['Content-Disposition'] = "attachment; filename=#{attachment.filename}"
+          header['Content-Disposition'] = attachment.content_disposition
           env['api.format'] = :binary
           attachment.diskfile.read
         end

spec/requests/api/v3/attachments/attachment_resource_shared_examples.rb

@@ -252,8 +252,10 @@ shared_examples 'an APIv3 attachment resource', type: :request, content_type: :j
     subject(:response) { last_response }
 
     context 'with required permissions' do
-      context 'for a local file' do
-        let(:mock_file) { FileHelpers.mock_uploaded_file name: 'foobar.txt' }
+      shared_examples 'for a local file' do
+        let(:mock_file) { raise "define mock_file" }
+        let(:content_disposition) { raise "define content_disposition" }
+
         let(:attachment) do
           att = FactoryBot.create(:attachment, container: container, file: mock_file)
 
@@ -270,7 +272,7 @@ shared_examples 'an APIv3 attachment resource', type: :request, content_type: :j
 
         it 'has the necessary headers' do
           expect(subject.headers['Content-Disposition'])
-            .to eql "attachment; filename=#{mock_file.original_filename}"
+            .to eql content_disposition
 
           expect(subject.headers['Content-Type'])
             .to eql mock_file.content_type
@@ -282,6 +284,20 @@ shared_examples 'an APIv3 attachment resource', type: :request, content_type: :j
         end
       end
 
+      context 'for a local text file' do
+        it_behaves_like 'for a local file' do
+          let(:mock_file) { FileHelpers.mock_uploaded_file name: 'foobar.txt' }
+          let(:content_disposition) { "inline" }
+        end
+      end
+
+      context 'for a local binary file' do
+        it_behaves_like 'for a local file' do
+          let(:mock_file) { FileHelpers.mock_uploaded_file name: 'foobar.dat', content_type: "application/octet-stream" }
+          let(:content_disposition) { "attachment; filename=#{mock_file.original_filename}" }
+        end
+      end
+
       context 'for a remote file' do
         let(:external_url) { 'http://some_service.org/blubs.gif' }
         let(:mock_file) { FileHelpers.mock_uploaded_file name: 'foobar.txt' }