Update a lead's information, such as contact details, assigned rep, status, or custom field values. You can also update or create related contacts (with phones/emails), appointments, notes, and custom fields all in a single request.

Relationship Management:

• Include an id field to update an existing related resource
• Omit the id field to create a new related resource
• This works for contacts, phones, emails, appointments, lead_notes, and lead_custom_fields