post https://sandbox.signup.nmi.com/api/v1/subscriptions
Creates a new subscription based on the provided data.
How signing requests work
When setting up, it's common to generate, store, and share a secret between your app and the app that wants to receive webhooks. The secret should be a random string, and how to create it is entirely up to you. The package will use the secret to sign a webhook call.
By default, the package will add a header called Signature that will contain a signature the receiving app can use if the payload hasn't been tampered with.