Cast incoming access_raw_diffs param to boolean

lib/api/merge_requests.rb

@@ -361,7 +361,7 @@ module API
           with: Entities::MergeRequestChanges,
           current_user: current_user,
           project: user_project,
-          access_raw_diffs: params.fetch(:access_raw_diffs, false)
+          access_raw_diffs: to_boolean(params.fetch(:access_raw_diffs, false))
       end
 
       desc 'Get the merge request pipelines' do

spec/requests/api/merge_requests_spec.rb

@@ -1542,9 +1542,9 @@ RSpec.describe API::MergeRequests do
         end
       end
 
-      context 'when access_raw_diffs is passed as an option' do
+      context 'when access_raw_diffs is true' do
         it_behaves_like 'accesses diffs via raw_diffs' do
-          let(:params) { { access_raw_diffs: true } }
+          let(:params) { { access_raw_diffs: "true" } }
         end
       end
     end