[FEATURE] Add support for proxy

[bavarezul13]

Hey! I’m playing with QuestDb and trying to ingest into it using the .Net client. I can connect to a local instance without issues, however, connecting to a remote server I get a 407. Connecting with the HttpClient is working by setting the correct proxy (in my case no proxy), however this Sender.New method does not accept passing anything related to proxy. I’ve tried setting the NO_PROXY=182.8.x.x…(server ip) environment variable, but still no success.

See the ip I'm using, if I change it to localhost, everything is fine :)

When working directly with HttpClient, I can manuallly set useProxy property: