feat: add support for NetBox 4.5+ v2 API tokens (Bearer auth)

[dsvetlov]

Summary

NetBox 4.5 introduced v2 API tokens with the format nbt_<key>.<plaintext>, which require the Bearer authorization keyword instead of the legacy Token keyword.

Currently, netbox-sync hardcodes Token in the Authorization header (module/netbox/connection.py), making it incompatible with v2 tokens on NetBox 4.5+.

This PR auto-detects the token version by checking the nbt_ prefix and uses the appropriate authorization keyword:

• nbt_* tokens → Authorization: Bearer <token>
• Legacy tokens → Authorization: Token <token> (fully backward compatible)

This matches how NetBox itself distinguishes token versions in netbox/api/authentication.py (V1_KEYWORD = 'Token', V2_KEYWORD = 'Bearer').

Changes

• module/netbox/connection.py: Detect token version by nbt_ prefix, use Bearer or Token accordingly
• README.md: Document v2 token support
• settings-example.ini: Add comment about v2 token format

Test plan

• Test with NetBox 4.5+ using a v2 token (nbt_ prefix) — sync completes successfully
• Test with NetBox using a legacy v1 token — backward compatibility confirmed
• Test with NetBox < 4.5 using a v1 token — no behavior change

[bb-Ricardo]

Hi, thank you. this looks good.

Would have one request: can you please add the comment from the the settings file here:

netbox-sync/module/netbox/config.py

Lines 26 to 33 in e972c94

	ConfigOption("api_token",
	str,
	description="""Requires an NetBox API token with full permissions on all objects except
	'auth', 'secrets' and 'users'
	""",
	config_example="XYZ",
	mandatory=True,
	sensitive=True),

Then you can autogenerate the config with

rm settings-example.ini
./netbox-sync.py -gc settings-example.ini