Update ReAuthorization call parameters (plutov#226)

License 2021

Add cancel billing agreement function (plutov#222)

Adding partner referral response (plutov#217)

* Adding links to refund response

* Adding partner referral response

Updating Order with missing fields (plutov#215)

* Update Order struct with API /v2 response fields according to the documentation https://developer.paypal.com/docs/api/orders/v2/\#orders_get

* Add order completed unmarshal response  unit test

Adding links to refund response (plutov#213)

Re-adding billing agreements endpoint (plutov#212)

* adding billing_agreements.go file

* added new types

* added tests

* added notice of deprecation

deletions made (plutov#209)

Added missing BillingAgreementId key in webhook (plutov#205)

* Added missing BillingAgreementId key in webhook

Webhook resource contains `billing_agreement_id`. Exists in type: `PAYMENT.SALE.COMPLETED` when a subscription is paid.

* review fix

Add create billing agreement from token (plutov#204)

* Add create billing agreement from token