Sets really don't preserve order. They might pretend to in some circumstances, but they don't so we really shouldn't rely on it at all. Also, freeze key sets as we don't support modifying them anyway, and improve some doc comments
I wonder whether we ought to make fixed route entries even more restrictive. Yes, they could contain multiple processors and links... but they never do because they're only useful when singular.
Sets really don't preserve order. They might pretend to in some circumstances, but they don't so we really shouldn't rely on it at all. Also, freeze key sets as we don't support modifying them anyway, and improve some doc comments