Delete a Contact Identifier

**This endpoint can be used to delete one identifier from a contact.** Deletion jobs are processed asynchronously. Note this is different from deleting a contact. If the contact has only one identifier, the asynchronous request will fail. All contacts are required to have at least one identifier. The request body field `identifier_type` must have a valid value of "EMAIL", "PHONENUMBERID", "EXTERNALID", or "ANONYMOUSID".