Skip CSRF referer check for cross-domain requests.

This commit extends the workaround in `cors_csrf` middleware
to Django Rest Framework's SessionAuthentication, which
calls Django's CSRF middleware directly.

The workaround checks the cross domain whitelist and
skips the CSRF referer check for domains on the whitelist.

Define TENDER_SUBDOMAIN so that we can still use vanity URLs

Update translations (autogenerated message)

Revert "To support UNICODE xblock.location"

Lms should be independent of mathjax

Unit page doesn't load when mathjax is down

This reverts commit 4856ef78, reversing
changes made to 7abbbb44.

Add Mocks to Enrollment API Doc Config

To support UNICODE xblock.location

When mathjax is down studio page doesn't work as
it wait for mathjax to load. I replaced the hard
dependency with soft dependency now unit page can
load with mathjax.

When cdn is down specially in the country like china
and others user face problem as application doesn't
work as intended. Instead of making mathjax hard
dependecy I have converted it into soft dependey
so that it won't cause user problem to use application
smothly if mathjax is not present.

TNL-1498

Fix Pylint violations (medium)

I can find no other record of this class.

Add coverage to openedx directory

Reduce query counts in FieldDataCache/DjangoKeyValueStore

Don't allow empty string or None for email.

Corrected data sent to E-Commerce API

Disable flaky lettuce test TNL-1679

Remove old comment from file

MA-345 Mobile Enrollment API: add course' Facebook URL.

decorate flaky test

Added Certificates Web/HTML View