Opencart script to accept orders from a post request from an affiliate

Create an Opencart 2.3.0.2 standalone script (PHP 7) that accepts an http post request as an order request from an affiliate. In conclusion, the script is going to act like a webhook for the affiliate.
The affiliate will place orders with the customer details and the product ids and quantities. The script will take the information and register an open order.
Ideally, the script will be in a separate folder as a single-file php script, calling all required Opencart libraries and files in order to receive the post request and register the order through the default Opencart functions. System setup is Opencart 2.3.0.2 running Journal 2(irrelevant) with no modifications.

(More details to be given. Detailed documentation of the HTTP Post request provided by the affiliate link)

REQUEST POST {webhook_url}

REQUEST HEADERS
-new order events

REQUEST PAYLOAD
-event_type (Type: String)
-event_time (Type: Date)
-order (Type: Object)
-changes (Type: Object) Order changes object -state (Type: Object)
-expires_at (Type: Object)
-dispatch_until (Type: Object)
-courier_voucher (Type: Object)
-courier_tracking_codes (Type: Object)

(More details to be given. Detailed documentation of the HTTP Post request provided by the affiliate link)