/// warn-code  = 3DIGIT
/// warn-agent = ( uri-host [ ":" port ] ) / pseudonym
///                 ; the name or pseudonym of the server adding
///                 ; the Warning header field, for use in debugging
///                 ; a single "-" is recommended when agent unknown
/// warn-text  = quoted-string
/// warn-date  = DQUOTE HTTP-date DQUOTE
/// ```
///
/// # Example values