Closes: #540 - Clarify Django bootstrap for portable schema export scripts

[bctiemann]

Closes: #540

Summary

• Expands the Exporting a Schema section with two explicit usage paths: manage.py nbshell (zero setup, recommended) and a standalone .py script that calls django.setup() before any imports.
• Adds an admonition explaining the AppRegistryNotReady error so users who encounter it have an immediate explanation and fix.

Addresses user report in discussion #534.

Test plan

• Docs render correctly via mkdocs serve
• Option B snippet works when run as python export_cot.py from /opt/netbox/netbox/

[pheus]

This is a useful docs improvement, but I don’t think we should merge the examples in their current form.

The current commands do not make it clear that they need to run in NetBox’s virtualenv. That’s an important detail for this type of documentation: users copying these examples with the system Python may hit import errors or dependency mismatches that look like issues with the export code itself.

We should also avoid presenting /opt/netbox as though it is the required installation path. It is a common example, but NetBox can be installed in other locations.

Please update the examples so they:

1. Treat /opt/netbox as an example NetBox installation root.
2. Activate NetBox’s virtualenv, or otherwise use the virtualenv Python.
3. Make clear that /path/to/export_cot.py is just the user’s script path.

For example:

# Replace this with your NetBox installation root.
export NETBOX_ROOT=/opt/netbox

source "$NETBOX_ROOT/venv/bin/activate"
cd "$NETBOX_ROOT"
PYTHONPATH="$NETBOX_ROOT/netbox" python3 /path/to/export_cot.py

With that clarified, the overall structure of the new section looks good.

[bctiemann]

Thanks for the clear feedback, Martin. Updated in 88c7891:

• Introduced a NETBOX_ROOT variable in both Option 1 and Option 2 so /opt/netbox is explicitly labelled as an example, not a required path.
• Option 2 now shows source "$NETBOX_ROOT/venv/bin/activate" before running the script, using your suggested bash snippet.
• Clarified that /path/to/export_cot.py is the user's script ("Where /path/to/export_cot.py is your script, containing:").
• Also folded in cleboo's suggestion from the issue: an all-COTs export snippet sits alongside the filtered one in Option 1.