Encode String for URL param or request body

String+Extensions.swift

//Both implementations thanks to https://useyourloaf.com/blog/how-to-percent-encode-a-url-string/
//Upgraded/cleaned up for Swift 4

Extension String {
    func percentEncodedForRFC3986() -> String? {
        let unreserved = "-._~/?"
        var allowed = CharacterSet.alphanumerics
        allowed.insert(charactersIn: unreserved)
        return self.addingPercentEncoding(withAllowedCharacters: allowed)
    }
  
    func x_www_form_urlencoded(encodeSpace: Bool = true) -> String? {
      let unreserved = "*-._"
      var allowed = CharacterSet.alphanumerics
      allowed.insert(charactersIn: unreserved)
        
      //encoding space is apparently optional
      if encodeSpace == false {
          allowed.insert(charactersIn: " ")
      }
        
      guard var encoded = self.addingPercentEncoding(withAllowedCharacters: allowed) else { return nil }
      if encodeSpace {
          encoded = encoded.replacingOccurrences(of: " ", with: "+")
      }
      return encoded
    }
}