/// <summary>Gets a <see cref="JwtHeaderDocument"/> which can be safely stored beyond the lifetime of the original object.</summary>
/// <returns></returns>
public JwtHeaderDocument Clone()
=> new JwtHeaderDocument(
_document.Clone(),
_alg.ValueKind == JsonValueKind.Undefined ? -1 : _alg.Idx,
_enc.ValueKind == JsonValueKind.Undefined ? -1 : _enc.Idx,
_kid.ValueKind == JsonValueKind.Undefined ? -1 : _kid.Idx,
_crit.ValueKind == JsonValueKind.Undefined ? -1 : _crit.Idx);
