Allow None value for NUM_PROXIES

[sarayourfriend]

Fixes

Related to #3398

Description

NUM_PROXIES needs to be able to be None to disable the feature. I got mixed up about the behaviour of 0 value for it and thought it was the same as None, but it's drastically different. None falls back to default, but 0 tells DRF to use the remote address (IP) of the request, which in the case of requests via proxy, is always the last proxy that handled the request. If you set it to 0, then everyone is getting throttled based on the proxy they went through, meaning they're sharing throttle quotas, rather than through their individual IP.

Testing Instructions

Run the application and use ipython to verify that NUM_PROXIES defaults to None:

In [1]: from conf.settings import rest_framework
In [2]: rest_framework.REST_FRAMEWORK
Out[2]: 
{'DEFAULT_AUTHENTICATION_CLASSES': ('oauth2_provider.contrib.rest_framework.OAuth2Authentication',),
 'DEFAULT_VERSIONING_CLASS': 'rest_framework.versioning.URLPathVersioning',
 'DEFAULT_RENDERER_CLASSES': ('rest_framework.renderers.JSONRenderer',
  'api.utils.drf_renderer.BrowsableAPIRendererWithoutForms'),
 'DEFAULT_THROTTLE_RATES': {'anon_burst': None,
  'anon_sustained': None,
  'anon_healthcheck': None,
  'anon_thumbnail': None,
  'oauth2_client_credentials_thumbnail': None,
  'oauth2_client_credentials_sustained': None,
  'oauth2_client_credentials_burst': None,
  'enhanced_oauth2_client_credentials_sustained': None,
  'enhanced_oauth2_client_credentials_burst': None,
  'exempt_oauth2_client_credentials': None},
 'EXCEPTION_HANDLER': 'api.utils.exceptions.exception_handler',
 'DEFAULT_SCHEMA_CLASS': 'api.docs.base_docs.MediaSchema',
 'NUM_PROXIES': None}

Checklist

• My pull request has a descriptive title (not a vague title likeUpdate index.md).
• My pull request targets the default branch of the repository (main) or a parent feature branch.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• [N/A] I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.
• [N/A] I ran the DAG documentation generator (if applicable).

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[krysal]

Confirmed it's None with the following commands ✅

just api/ipyhon

from rest_framework.settings import api_settings
print(api_settings.NUM_PROXIES)

It was returning 0 on main.

[AetherUnbound]

LGTM and local commands load the setting as None appropriately!