Update an existing custom field
API key required in Authorization header. Format: iclosed-<token>
x >= 11000100010001000NUMBER, TEXT, TEXT_AREA, DATE, USER, USERS_MULTIPLE, URL, SINGLE_SELECT, MULTIPLE_SELECT, EMAIL, RATING CONTACT, CALL, EVENT, DEAL, USER, ISCORE, UNIFIED_INBOX, INVITEE_QUESTION Date field configuration when time is selected.