post https://api-gateway.sandbox.ngenius-payments.com/identity/auth/access-token
The first step for any Online gateway interaction is to validate ourselves with the identity service and obtain an access token. This token allows us to execute operations on the gateway APIs with authority, and whilst a single token will expire after 5 minutes, we can use our Service Account API key to generate one at any time. Please pass your API key in the authorization header prefixed with Basic and a space