optionalHeaderValuePF
Calls the specified partial function with the first request header the function is isDefinedAt and extracts the result of calling the function.
Signature
def optionalHeaderValuePF[T](pf: PartialFunction[HttpHeader, T]): Directive1[Option[T]]
Description
The optionalHeaderValuePF directive is similar to the headerValuePF directive but always extracts an Option value instead of rejecting the request if no matching header could be found.