Opaque handle for one cancelable unary HTTP execution.

Sessions are created by ExecutionPlane.HTTP.start_unary/2. The process that starts a session is its result owner and must call ExecutionPlane.HTTP.await_unary/2. Cancellation may be triggered from another BEAM process with ExecutionPlane.HTTP.cancel_unary/2.

The request identifier is an implementation detail of the lower :httpc transport and must not be persisted or treated as a durable execution ref.