get https://{environment}.{server}.com/v3/token/external-
Get a payment method using its External ID. For example doing an HTTP get call to [base_url]/token/external-abc will retrieve a payment method using the user defined External ID of 'abc'.
When tokenizing a payment method, it is possible to add an External ID. The External ID can be any alphanumeric string. Payment methods can then be looked up based on the External ID that was set during creation. Simply Prepend the External ID with 'external-'.