withHeader method
Returns a copy with name replaced by one value.
Implementation
AcpHttpHeaders withHeader(String name, String value) {
_validateHeader(name, value);
final copy = Map<String, _HeaderValues>.of(_entries);
copy[name.toLowerCase()] = _HeaderValues(name, <String>[value]);
return AcpHttpHeaders._(Map<String, _HeaderValues>.unmodifiable(copy));
}