def validate_value(value)
      v = value.to_s
      return v unless v.include?("\n")
      raise HeaderError, "Invalid HTTP header field value: #{v.inspect}"
    end
def validate_value(value)
      v = value.to_s
      return v unless v.include?("\n")
      raise HeaderError, "Invalid HTTP header field value: #{v.inspect}"
    end
Ensures there is no new line character in the header value

 @param [String] value
 @raise [HeaderError] if value includes new line character
 @return [String] stringified header value