withAddedHeader method
Returns a copy with value appended under name.
Implementation
AcpHttpHeaders withAddedHeader(String name, String value) {
_validateHeader(name, value);
final key = name.toLowerCase();
final existing = _entries[key];
final copy = Map<String, _HeaderValues>.of(_entries);
copy[key] = _HeaderValues(existing?.name ?? name, <String>[
...?existing?.values,
value,
]);
return AcpHttpHeaders._(Map<String, _HeaderValues>.unmodifiable(copy));
}