search api shixun add identifier column

app/models/searchable/shixun.rb

@@ -43,6 +43,7 @@ module Searchable::Shixun
   def to_searchable_json
     {
       id: id,
+      identifier: identifier,
       author_name: user.real_name,
       author_school_name: user.school_name,
       visits_count: visits,
@@ -55,4 +56,4 @@ module Searchable::Shixun
       { user: { user_extension: :school } }
     end
   end
-end
+end