Add property to endpoint.request to indicate when the request may be made without params

[razor-x]

Some endpoints can be called without any parameter (or an empty body). This should be make available in endpoint.

Endpoint specs that have all params marked as optional may still require at least one param, so most likely endpoints need to be annotated when they support this.

This will allow API and SDKs to indicate this, e.g., add proper validation and types.