note that there are two URL's in play here, the first is the http:// (or
https://) URLs which do not necessarily map code entity tree using the standard
syntax, e.g.:

 http://gudangapi.com/ga/tax.id.npwp/validate_npwp

while the code entity URI is: /tax/id/npwp/validate_npwp

the client should find out the code entity URI then convert it to riap+http://
scheme. E.g.

 riap+http:/tax/id/npwp/validate_npwp?url=http://gudangapi.com/ga/tax.id.npwp/validate_npwp

or perhaps encode the whole HTTP url inside 'host':

 riap+http://(base64-encode(http://gudangapi.com/ga/tax.id.npwp/validate_npwp))/tax/id/npwp/validate_npwp

This way, we can play with the path in the riap+http:// safely.