A rendered header value. undefined means absent by state: the resolver
selected the header, but the state it renders from does not exist (no routing
map yet, no USDID registered, no user id for a templated value, …), so the
header is omitted instead of being invented.
A rendered header value.
undefinedmeans absent by state: the resolver selected the header, but the state it renders from does not exist (no routing map yet, no USDID registered, no user id for a templated value, …), so the header is omitted instead of being invented.