Attributes

contacts[array]
contact_id
Example: c-###-####
external_id

Example Object

{
   "contacts" : [
      {
         "contact_id" : "c-###-####",
         "external_id" : "..."
      },
      {
         "contact_id" : "c-###-####",
         "external_id" : "..."
      }
   ]
}