fix: use common default for LANGUAGE_COOKIE_NAME

[cmltaWt0]

Changes:

• effectively use default LANGUAGE_COOKIE_NAME value from common.py for cases when there is no
  LANGUAGE_COOKIE and LANGUAGE_COOKIE_NAME in ENV_TOKENS

Description

Fix regression introduced in https://github.com/edx/edx-platform/pull/28796
The defaults from lms/envs/common.py and cms/envs/common.py aren't used.
This causes login exception in case LANGUAGE_COOKIE_NAME is absent in ENV_TOKENS.
Actually this happened for tutor installation overhangio/tutor#507 and avoided temporary by settings LANGUAGE_COOKIE_NAME in common_all.py for maple release.

Supporting information

Original PR: https://github.com/edx/edx-platform/pull/28796

Testing instructions

To test it in devstack just remove LANGUAGE_COOKIE from /edx/etc/lms.yml and try to login into LMS or Studio.

root@lms:/edx/app/edxapp/edx-platform# cat $LMS_CFG | grep LANGUAGE_COOKIE
LANGUAGE_COOKIE: openedx-language-preference

Login to the LMS and get the Error:

edx.devstack.lms                  | 2021-10-23 12:45:08,090 ERROR 269 [root] [user 8] [ip 172.28.0.1] signals.py:22 - Uncaught exception from None
edx.devstack.lms                  | Traceback (most recent call last):
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
edx.devstack.lms                  |     response = get_response(request)
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/utils/deprecation.py", line 119, in __call__
edx.devstack.lms                  |     response = self.process_response(request, response)
edx.devstack.lms                  |   File "/edx/app/edxapp/edx-platform/openedx/core/djangoapps/lang_pref/middleware.py", line 93, in process_response
edx.devstack.lms                  |     response.delete_cookie(
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/http/response.py", line 252, in delete_cookie
edx.devstack.lms                  |     key.startswith(('__Secure-', '__Host-')) or
edx.devstack.lms                  | AttributeError: 'NoneType' object has no attribute 'startswith'
edx.devstack.lms                  | Internal Server Error: /api/user/v1/account/login_session/
edx.devstack.lms                  | Traceback (most recent call last):
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
edx.devstack.lms                  |     response = get_response(request)
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/utils/deprecation.py", line 119, in __call__
edx.devstack.lms                  |     response = self.process_response(request, response)
edx.devstack.lms                  |   File "/edx/app/edxapp/edx-platform/openedx/core/djangoapps/lang_pref/middleware.py", line 93, in process_response
edx.devstack.lms                  |     response.delete_cookie(
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/http/response.py", line 252, in delete_cookie
edx.devstack.lms                  |     key.startswith(('__Secure-', '__Host-')) or
edx.devstack.lms                  | AttributeError: 'NoneType' object has no attribute 'startswith'
edx.devstack.lms                  | 2021-10-23 12:45:08,183 ERROR 269 [django.request] [user 8] [ip 172.28.0.1] log.py:224 - Internal Server Error: /api/user/v1/account/login_session/
edx.devstack.lms                  | Traceback (most recent call last):
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
edx.devstack.lms                  |     response = get_response(request)
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/utils/deprecation.py", line 119, in __call__
edx.devstack.lms                  |     response = self.process_response(request, response)
edx.devstack.lms                  |   File "/edx/app/edxapp/edx-platform/openedx/core/djangoapps/lang_pref/middleware.py", line 93, in process_response
edx.devstack.lms                  |     response.delete_cookie(
edx.devstack.lms                  |   File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/http/response.py", line 252, in delete_cookie
edx.devstack.lms                  |     key.startswith(('__Secure-', '__Host-')) or
edx.devstack.lms                  | AttributeError: 'NoneType' object has no attribute 'startswith'
edx.devstack.lms                  | [23/Oct/2021 12:45:08] "POST /api/user/v1/account/login_session/ HTTP/1.1" 500 311151

LanguagePreferenceMiddleware do the following:

response.delete_cookie(
    settings.LANGUAGE_COOKIE_NAME,
    domain=settings.SHARED_COOKIE_DOMAIN
)
caused an Exception due to absence of LANGUAGE_COOKIE_NAME settings variable

Also there are tons of code in the platform with direct accessing to the lang setting as settings.LANGUAGE_COOKIE_NAME

[openedx-webhooks]

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[edx-status-bot]

Your PR has finished running tests. There were no failures.

[natabene]

@cmltaWt0 Thank you for your contribution. Is this ready for our review?

[cmltaWt0]

@cmltaWt0 Thank you for your contribution. Is this ready for our review?

Yes. It's ready.

[dianakhuang]

Thanks so much for this fix!

[openedx-webhooks]

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[edx-pipeline-bot]

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[edx-pipeline-bot]

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