We have released our newer version of Product Keys Delivery (PKD) for Magento 2.x which has many improvements but with a major feature called Post To An API. The Post to an API feature allows you to send your keys to 3^rd party systems along with other required information using REST API protocol. You can use with any type of authentication that your 3^rd party system requires such as API Key, Basic Auth or Bearer Token. You can flexibly use one of methods from POST, PUT or GET.