Don't hit db to access user_id in TokenProxy

[zaslavskii]

Description

When using nplusone middleware from https://github.com/jmcarp/nplusone, the error occurs if one tries to access Token app in django admin.

This happens due to recursive DB calls, as the user id is accessed through the user object rather than through user_id field.

Not sure if it's a problem of DRF itself, but the following change fixes the problem as well as reduces DB hits.

jmcarp/nplusone#38

[lovelydinosaur]

Okay, I actually had to look this up in the note here... https://docs.djangoproject.com/en/3.1/topics/db/models/#field-name-hiding-is-not-permitted

Some fields define extra attributes on the model, e.g. a ForeignKey defines an extra attribute with _id appended to the field name, as well as related_name and related_query_name on the foreign model.

Do the Django docs mention the <field>_id attribute elsewhere, or only in that passing note?

[zaslavskii]

https://docs.djangoproject.com/en/3.1/topics/db/optimization/#use-foreign-key-values-directly

[lovelydinosaur]

Right, makes sense. Thanks!