Changes to Create a refund session

the currency request property's minLength was increased from 0 to 3

added the pattern ^[A-Za-z]{3}$ to the request property currency

the error/code response's property type changed from string to no type for status 400

the currency request property's maxLength was set to 3

removed the optional property error/errors from the response with the 400 status

added the new optional request property merchant_id

added the optional property error/metadata to the response with the 400 status

added subschema #1 subschema #2 to the error/code response property allOf list for the response status 400

endpoint added

api path removed without deprecation