pub fn header<'a>(
map: &'a BTreeMap<String, String>,
name: &str,
) -> Option<&'a str>Expand description
Case-insensitive header lookup.
HTTP header names are case-insensitive on the wire (RFC 9110). The
fixtures store them lower-cased by convention, but rules call
header(headers, "Authorization") and header(headers, "x-signature")
interchangeably — this helper makes both work.
Returns the value of the first matching header. Iteration order is
stable because BTreeMap is ordered, but in practice header
names are unique within a case fixture.