struct NaturalMethodTypes

|NaturalMethodTypes| contains information about an interaction:

When |FidlMethod| has a request (including events) with a body:

- Request: the natural domain object representing the request body.

When |FidlMethod| has a response with a body:

- Response: the natural domain object representing the response body.

When |FidlMethod| is two-way:

- Completer: the completer type used on servers.

- ResultCallback: the callback type for the corresponding asynchronous call.