resolve teacher role_id dynamically instead of hardcoding ObjectId

lib/tasks/sync_nfu_personal_data_tasks.rake

@@ -736,10 +736,10 @@ module NfuSyncPlugin
 
     def sync_teacher_attribute(member, config)
       # 比對或建立 attribute_field
-      role_id = BSON::ObjectId('6904852a4eae35f6d58a443f')
-      
+      teacher_role = Role.where(:'title.en' => /teacher/i).first   
+      return unless teacher_role                                    
+      role_id = teacher_role.id                                     
       attribute_field = AttributeField.where(:role_id => role_id, 'title.zh_tw' => config[:title_zh_tw]).first
-      
       unless attribute_field
         # 自動建立 attribute_field
         attribute_field = AttributeField.new