POST /buyers API. The call accepts
an optional external_identifier (for example the user’s email, username, or a
database ID) and an optional display_name which will be shown in the admin
panel.
A buyer can be created without any
external_identifier and display_name. In
that case, the buyer only serves as a way to link stored payment methods to a
user ID. In this situation, you will need to keep track of the buyer’s ID in your
database to link it back to a user record.POST /buyers