Use this endpoint to create or update person records, using a unique attribute to search for existing People (for example the email_addresses attribute). If a person is found with the same value for the matching attribute, that person will be updated. If no person with the same value for the matching attribute is found, a new person will be created instead. If you would like to avoid matching, please use the Create person endpoint.
If the matching attribute is a multiselect attribute, new values will be added and existing values will not be deleted. For any other multiselect attribute, all values will be either created or deleted as necessary to match the list of supplied values.