Send an invitation to a single recipient. Note that this is a premium endpoint and is not available on all plans.

If you are using the Organisation Hierarchy feature, to assign a recipient to an entity within the hierarchy, supply either entity_id or entity_unique_id (not both); the entity must be active and belong to your organisation.

If entity auto-insert is enabled for your organisation and this contact list's custom columns are mapped to entity fields, the mapped custom_columns values are also written to an entity that entity_unique_id creates.

On an SMS invitation, a mobile number that has opted out of SMS messages from this sender is not sent to, stored or charged; it comes back in failed_contacts with status_code``OPTOUT in a 200 response that charges nothing. When the invitation could not be sent, the 500 response carries failed_contacts too.