Optimize user fetching in TokenAuthentication

[eshaan7]

From django-silk profiling,

        if not auth_token.user.is_active:

is causing a query like:

SELECT "api_user"."id",
       "api_user"."password",
       "api_user"."last_login",
       "api_user"."is_superuser",
       "api_user"."username",
       "api_user"."first_name",
       "api_user"."last_name",
       "api_user"."email",
       "api_user"."is_staff",
       "api_user"."is_active",
       "api_user"."date_joined"
FROM "api_user"
WHERE "api_user"."id" = 1
LIMIT 21

this can be potentially be optimized using select_related.

[eshaan7]

Another idea could be a way by which user can configure the select_related field for request.user on the TokenAuthentication class.

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Reference: https://stackoverflow.com/a/65924551/10534470