Accelerator idempotency handler needs an extension to handle requests that create resources inside the server (POST) but having an empty payload

[Akila94]

According to the current idempotency validation implementation, the method used to validate the idempotency of requests with empty payloads is written in a way that cannot be extended by the toolkits. There can be POST requests that don't have a request body (basically an empty JSON ({})). But still, these requests could create a resource inside the server.

A perfect example is the start authorization POST request of the NextGenPSD2 Implementation Guidelines. The request doesn't have a payload but still creates a resource inside the server. Making it non-idempotent. This request is used in multi-level authorization scenario in the NextGenPSD2 toolkit.

Definition of Idempotent Request

An HTTP method is considered idempotent if the intended effect on the server of making a single request is the same as the effect of making several identical requests.

Therefore, we need to expose an extension from the accelerator idempotency validator so the toolkits has such requests can be marked as non-idempotent requests.