Merge branch 'fj-reduce-gitaly-calls-snippet-rest-endpoints' into 'master'

Reduce number of gitaly calls in Snippet REST list endpoints

See merge request gitlab-org/gitlab!63735

lib/api/entities/snippet.rb

@@ -5,16 +5,22 @@ module API
     class Snippet < BasicSnippet
       expose :author, using: Entities::UserBasic
       expose :file_name do |snippet|
-        snippet.file_name_on_repo || snippet.file_name
+        snippet_files.first || snippet.file_name
       end
       expose :files do |snippet, options|
-        snippet.list_files.map do |file|
+        snippet_files.map do |file|
           {
             path: file,
             raw_url: Gitlab::UrlBuilder.build(snippet, file: file, ref: snippet.repository.root_ref)
           }
         end
       end
+
+      private
+
+      def snippet_files
+        @snippet_files ||= object.list_files
+      end
     end
   end
 end