Configure absolute and server URL prefixes

[manics]

This started off as a fix for the X-Forwarded-Context X-ProxyContextPath. Previously they were always /proxy/{port}, now they should be /server-name if this is a managed server. Since this is related to the code that controls the URL rewriting I thought I'd add in support for absolute URLs.

I've done some testing with:

c.ServerProxy.servers = {
    'python-http': {
        'command': ['python3', '-m', 'http.server', '{port}'],
    },
    'python-http-abs': {
        'command': ['python3', '-m', 'http.server', '{port}'],
        'rewrite': '',
    },
}

python-http should produce logs like

"GET / HTTP/1.1" 200 -

python-http-abs should produce logs like

"GET /python-http-abs/ HTTP/1.1" 404 -

Also /proxy-abs/port is the absolute version of /proxy/port

Needs more testing! @jacobtomlinson @psychemedia

Closes #43

[manics]

I've changed the config name from absolute: False|True to rewrite: "/"|"" to match the terminology typically used when configuring web-servers and proxies, e.g. https://github.com/kubernetes/ingress-nginx/tree/nginx-0.21.0/docs/examples/rewrite

The prefix for ports without rewriting is still /proxy-abs/port though alternatives could be /proxyp/{port} (for proxy-passthrough) or /passthrough/{port}. What do you think?

[yuvipanda]

w00t, this is awesome. I'll try take a closer look later today.

Vague first thoughts:

1. Are there ways we can do this without extra classes / inheritance?
2. How about /proxy/absolute? That way we can do /proxy/<options-string> later if need be.

[manics]

Are there ways we can do this without extra classes / inheritance?

Yes, I think it's possible to combine the classes and use a more complex URL match, I'll give it a go

How about /proxy/absolute

👍

[manics]

Oops accidentally closed this .... reopened at #85