pub const REQUEST_CANCELLED: u64 = _; // 1u64Expand description
The application error code a request stream is reset with when the
requester abandons it: CANCELLED, 0x1.
Draft-17 removed UNSUBSCRIBE and FETCH_CANCEL and draft-20 has not brought
them back. Cancelling a request is resetting the bidirectional stream it
was made on, and CANCELLED is the code draft-20 assigns for “the stream
was cancelled by either endpoint” — see StreamResetErrorCode::Cancelled.
Taken from the codec’s own registry rather than written as a literal so a
renumbering in a later draft cannot be missed here.
This is what RequestStream::cancel uses when no code is chosen for it,
and what RequestStream’s Drop sends.