docs: Update Token Authentication sections to explain how to properly…

[dontic]

… disable it

Background (can be skipped)

Just as an FYI for anyone who might be looking for this exact issue.

I was using drf-spectacular together with dj-rest-auth and was getting a constant error:

File "/root/.local/share/virtualenvs/facturing-be-yU94o058/lib/python3.11/site-packages/rest_framework/utils/model_meta.py", line 35, in get_field_info
    opts = model._meta.concrete_model._meta
           ^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute '_meta'

The problem was that I was not using Token Authentication but rather Session Authentication, and thus, following the docs, I set TOKEN_MODEL to None.

The problem comes when the TokenSerializer is still active, and tries to get the Token model, which is overridden by the TOKEN_MODEL setting. This causes the error above.

Fix

To properly disable Token Authentication, the TOKEN_SERIALIZER setting should also be set to None, together with TOKEN_MODEL.

I've added a couple of notes under TOKEN_SERIALIZER and TOKEN_MODEL specifying that both need to be set to None in order to fully disable the Token Authentication functionality.