Header related regular expressions (based on amphp/http package)
Note: header delimiter (\r\n) is modified to \r?\n to accept line feed only delimiters for BC reasons.
@license https://github.com/amphp/http/blob/v1.0.1/LICENSE
https://github.com/amphp/http/blob/v1.0.1/src/Rfc7230.php#L12-L15
public const HEADER_REGEX = "(^([^()<>@,;:\\\"/[\\]?={}\x01- ]++):[ \t]*+((?:[ \t]*+[!-~\x80-\xff]++)*+)[ \t]*+\r?\n)m";