1. The only out of the box ways to create users is through the [admin tool](https://community.denodo.com/docs/html/browse/7.0/vdp/administration/databases_users_and_access_rights_in_virtual_dataport/administration_of_databases_users_roles_and_their_access_rights/creating_users), or through [VQL](https://community.denodo.com/docs/html/browse/6.0/vdp/vql/creating_databases_users_roles_and_access_privileges/creating_users/creating_users). So, to have a web service that does this, I might suggest creating a base view over vdp that [accepts parameters](https://community.denodo.com/answers/question/details?questionId=9060g0000004ElXAAU&title=How+to+create+base+view+which+accepts+parameter), with VQL to create users. You can then publish that base view on a web service, and voila, web service to create users!
2. It sounds like you’re looking for [Auditing User Access](https://community.denodo.com/kb/view/document/Auditing%20User%20Access%20in%20Virtual%20DataPort?category=Security), which will provide connection information to vdp, through apis or otherwise.
3. Auth doesn’t go in the URL, it goes in the header. You would be sending auth credentials in plaintext otherwise, and an https connection will be able to encrypt the header in transit.
Hope this helps!