Fixes #304: Change Record._endpoint_from_url() URL parsing to support other paths for NetBox than root

[markkuleinio]

This is to support NetBox API base URLs with one or more directories. In those cases the previous code picked incorrect parts from the URL.

Fixes #304.

[zachmoody]

Ha, was just about to respond to you in the issue saying I hoped to make some time next week to work on the laundry list of issues that have piled up. You beat me to this one :)

Only concern with this approach is the paths that don't conform to what we're expecting like /ipam/prefixes/:id/available-ips/. I'm just spit-balling here, but wonder if we anchored the index on /api/ if we could get more predictable results. 🤔

Adding a test for that and the directory URLs in test_endpoint_from_url would be great too.

[markkuleinio]

Would it be safe to first remove self.api.base_url from url and then get the app and endpoint after that?

[zachmoody]

Good stuff, thanks as always @markkuleinio.