Finished feature DBOARD3-439-new-lnetd-endpoint.

docs/source/protocol/index.rst

docs/source/protocol/lnetd.rst

inventory_provider/__init__.py

inventory_provider/routes/common.py

inventory_provider/routes/lnetd.py

inventory_provider/routes/poller.py

test/per_router/test_lnetd_routes.py

test/test_general_lnetd_routes.py