Transfer ownership through webui

[jakob1379]

Is your feature request related to a problem? Please describe.
I figured you can transfer ownership of a VPN through the rest API after searching through the webUI without finding the option to do so.

Describe the solution you'd like
Being able to transfer ownership as an additional attribute to a user.

Describe alternatives you've considered
simply document how to do so in the documentation and keep it a REST API-only option. Currently an undocumented feature.