There are four different methods used in the API to create, read, update, and list checkout recources.
The authorization used is basic authentication and you need a merchant id and an api key to call these methods. The parameters are used to create an auth-string which is used in the message headers to authorize calls.
Auth-string = Base64 representation of “merchant_id:api_key”
merchant_id = 1234
api_key = dc157182-e25a-4008-bd09-903df3428db4
Combined these give us a credential string:
Which base64-encoded gives us the auth-string: