Parse f5vpn urls

[fwiesel]

After an endpoint-inspection, the webpage forwards
to an f5vpn url, which can now be passed on to
gof5 to extract the session-id itself.

Only missing to be a proper f5vpn handler is
logging

[kayrus]

@fwiesel can you provide an f5vpn URL example? I haven't seen it before.

[fwiesel]

Sure, it seems to have the following pattern:
f5-vpn://<server-fqdn>?server=<server-fqdn>&resourcename=<resource-path-with-slashes>&resourcetype=network_access&cmd=launch&protocol=https&port=443&sid=<32*n>&token=<32-hex>&otc=<32-hex>&otc=<32-hex>

I assume, OTC seems to stand for one-time-code, and we get two of them. The sid is presumably session-id, and it is bogus, as we provide it.

[chadcatlett]

Just as a voice of support for this PR. For nearly two months I've been using this PR to enable me to use gof5 with a F5 VPN endpoint that uses a web page based authentication flow.

It has consistently worked 100% of the time.