To do this you'll need to know the ID of the contact which you'll use to construct the URL when POST/PUTing a byte stream containing the attachment file.
https://com/api.xro/2.0/Contacts/ Use this method to create one or more contact records.
All updates (PUTs) are full replacements of the contact properties.
Create a new contact in Hub Spot with a simple HTTP POST to the Contacts API.
Cannot be set via PUT or POST - it is automatically set when an accounts payable invoice is generated against this or false – Boolean that describes if a contact has any AR invoices entered against them.
It may be of benefit in relieving other mental health concerns as well, including attention deficit-hyperactivity disorder (ADHD), although more research is needed.
An available option is to sell your spot to a friend who is able to attend.