As inputRequired, but also attaches an opaque requestState
(SEP-2322): a stateless draft server encodes whatever context it needs
to resume the call into this blob, which the client echoes verbatim on
the retry and the handler reads back via RequestContext.requestState.
As inputRequired, but also attaches an opaque requestState (SEP-2322): a stateless draft server encodes whatever context it needs to resume the call into this blob, which the client echoes verbatim on the retry and the handler reads back via RequestContext.requestState.