Vertx WebClient should support HTTP proxy server proxying HTTPS requests

[sberyozkin]

Description

Original question: https://stackoverflow.com/questions/76962454/quarkus-vert-x-attempting-to-connect-to-proxy-over-ssl.

Keycloak address is HTTPS based. Squid proxy is HTTP based but HTTPS is attempted between Quarkus and Squid.

I'm marking it as an enhancement as I'm not sure if it is a bug or if the whole concept of HTTP proxy proxying HTTPS requests is very sound from the security point of view.

Additional info:
https://serverfault.com/questions/1113988/how-does-a-http-proxy-server-proxy-https-requests
(the comment to that unanswered question points to another useful doc)

CC @cescoffier @vietj @tsegismont

Implementation ideas

No response

[sberyozkin]

Opened it in the right repository: vert-x3/vertx-web#2468