add maintainer to the project partial

app/views/api/v1/projects/_project.json.jbuilder

@@ -2,3 +2,8 @@ json.(project, :id, :name)
 json.fullname project.name_with_owner
 json.url api_v1_project_path(project.id, format: :json)
 json.git_url git_repo_url(project.name_with_owner)
+json.maintainer do
+  if project.maintainer
+    json.partial! 'api/v1/maintainers/maintainer', maintainer: project.maintainer
+  end
+end

app/views/api/v1/projects/show.json.jbuilder

@@ -5,7 +5,9 @@ json.project do
   json.updated_at @project.updated_at.to_i
   json.partial! 'api/v1/shared/owner', owner: @project.owner
   json.maintainer do
-    json.partial! 'api/v1/shared/member', member: @project.maintainer
+    if @project.maintainer
+      json.partial! 'api/v1/maintainers/maintainer', maintainer: @project.maintainer
+    end
   end
 
   json.project_statistics @project.project_statistics do |statistic|