Add tests for HTTP redirect responses to the interceptor

[arschles]

The interceptor uses the standard library's single host reverse proxy. This proxy should handle HTTP redirect responses automatically, but a test should be added to the interceptor to ensure that is the case, and the redirects are processed properly.

The client of the interceptor should not see evidence of the redirect.

[arschles]

@yaron2 we discussed this offline. in your opinion, should the interceptor handle redirections? As expected, the standard library's reverse proxy code doesn't follow redirects. I don't think we should have the interceptor follow them either, because it should be left up to the client how to react to a 302, 301, or similar. Maybe one exception to this could be to follow redirects to other internal microservices.

WDYT?

[yaron2]

I'm fine not supporting redirects and gather feedback if this is needed.

[arschles]

Thanks @yaron2 for letting me know