MICROBA-905 Add django-simple-history  to CertificateInvalidation model

* Don't show marketing links if not configured

* Remove failing test

Applied pylint amnesty

[MST-636] Add additional check for proctoring requirements

Introduce and use a roles_api module, use the roles API in receivers that want to create or delete role assignments.
For new learners and admins, associate their user-role with the customer to which they are linked.
Does not yet specify the enterprise_customer for deletions. We want to maintain current behavior on deletes until we do a data backfill of that field. So for now, we'll continue to delete all assignments held by the deleted user.
Install django-cache-memoize, so that we can memoize roles (not assignments) in the Django cache.

VAN-308

[BD-21] Upgrade usage of edx_toggles.toggles

Applied pylint-amnesty to openedx apps

BOM-2329: Applied pylint-amnesty to system_wide_roles, theming, user_…

BOM-2330: Applied pylint-amnesty to util, verified_track_content, vid…

BOM-2331: Applied pylint-amnesty to waffle_utils, xblock, xmodule_dja…

BOM-2335

BOM-2336

BOM-2331: Applied pylint-amnesty to waffle_utils, xblock, xmodule_django, zendesk_proxy, __init__.py

Apply pylint-amnesty.

Apply pylint-amnesty.

Applied pylint-amnesty to common/djangoapps/entitlements

* pylint amnesty in course apps under openedx

* pylint amnesty in demographics, discussions and comments app

* pylint amnesty in openedx apps

The waffle classes previously in future are now available directly from
edx_toggles.toggles. Since this future module is going to be removed soon,
we become future-proof by getting rid of it.

Applied pylint-amnesty to util

Applied pylint-amnesty to courseware

Applied pylint-amnesty to course_api

Applied pylint-amnesty to openedx/core/djangoapps/{session_inactivity_timeout, signals, site_configurations}

update thresolds after IM security fixes 7