inventory plugin: support netbox endpoints running in a non-root context path (subpath)

[lanefu]

Related Issue

#1408

New Behavior

Updated Plugin to parse the full path of the netbox server and compose API endpoints accordingly.
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allow inventory to support netbox endpoints on host.example.com/netboxpath/

This is a patch I originally made for v3.13 which had updated parsing of the openapi endpoint and assumes that netbox is always running in the root context rather than a path. This performs the additional url parsing to derive the correct inventory API endpoints if netbox is running on a path rather than a root context.

I've tested this rebased patch on latest netbox running on in the root context path, as well as my legacy deployment running on host.com/netbox/
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Discussion: Benefits and Drawbacks

• allows users to run in additional supported configurations ex: somehost.example.com/netbox/ rather than only netbox.example.com

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Changes to the Documentation

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Proposed Release Note Entry

update inventory plugin to support netbox API running on non-root context paths.
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Double Check

• I have read the comments and followed the CONTRIBUTING.md.
• I have explained my PR according to the information in the comments or in a linked issue.
• My PR targets the devel branch.

[lanefu]

Also related to #1195

[lanefu]

For some additional background in response to #1195

When I originally implemented this fix a year ago, I had already been using netbox inventory and ipam modules for quite a while (using a subpath) The inventory plugin broke when some changes were made in response to querying OpenAPI.

However, from what I recall, it only broke the inventory plugin... The other modules relying on the netbox_util module already had better api path parsing and it just worked. My solution was inspired from what was in netbox_util

ansible_modules/plugins/module_utils/netbox_utils.py

Line 857 in cd0b654

response = open_url(base_url + "/docs/?format=openapi")

[sc68cal]

The integration test failure against 4.2 is unrelated to this change (it's an issue with how NetBox reports its versions in that branch, it's a regression), and the doc build failure is unrelated to this change as well. I think this is good to go.

[leitwerk-ag]

Oh, I'd love to see this one merged 😍

[sc68cal]

@rodvand I'm planning on merging this regardless of the CI failure, which is unrelated to this change. Thoughts?