* refactor: pyupgrade in common/lib/xmodule

Co-authored-by: Usama Sadiq <usama.sadiq@arbisoft.com>

* refactor: pyupgrade on common/lib

Co-authored-by: Usama Sadiq <usama.sadiq@arbisoft.com>

pyupgrade in calendar-sync. 

= IMPORTANT WARNING =

This can be a VERY EXPENSIVE MIGRATION which may take hours or
days to run depending on the size of the courseware_studentmodule
table on your site. Depending on your database, it may also lock
this table, causing courseware to be non-functional during that
time.

If you want to run this migration manually in a more controlled
way (separate from your release pipeline), the SQL needed is:

  CREATE INDEX `courseware_stats` ON `courseware_studentmodule`
     (`module_id`, `grade`, `student_id`);

You can then fake the migration:
  https://docs.djangoproject.com/en/2.2/ref/django-admin/#cmdoption-migrate-fake

= Motivation and Background =

TLDR: This adds an index that will speed up reports like the
Problem Grade Report. This fixes a performance regression that
was unintentionally introduced in 25da206c.

I'm capturing the entire saga below, in case Open edX operators
need to dig into it.

The tale begins in November of 2012 (yes, seriously). We had an
inline analytics feature that would display a histogram to course
staff by each problem in the LMS, detailing how students did on
that problem (e.g. 80% got 2 points, 10% got 1 point, 10% got 0
points). The courseware_studentmodule table already had an index
on the module_id (a.k.a. module_state_key), but because there
were 100K+ students that had student state for some problems,
the generation of those histograms was still extremely expensive.
During U.S. Thanksgiving weekend in late November of 2012, that
load started causing operational failures on edx.org.

As an emergency measure, I manually added a composite index for
(module_id, grade, student_id) on courseware_studentmodule in
order to stabilize the courseware on edx.org. I did _not_ follow
up properly and add it in a migration file. Later on, the inline
analytics feature was removed entirely, so the index was considered
redundant (but again, it was not properly cleaned up).

Various reports were created over the years, some of which
relied on having an index for module_id. These ran fine because
there had long been an index for that field specifically.

In 2018, the courseware_studentmodule table for edx.org ran into
the 2 TB size limit that our old RDS instance had. We had a fair
amount of monitoring for various limits that we thought we might
run into, but the per-table limit took us by surprise. The Devops/
SRE person fielding that issue needed to free up space in a hurry
in order to make the courseware functional again. Examining the
database itself, he noticed that we had a module_id index that was
technically redundant because the composite index of (module_id,
grade, student_id) would cover queries that would otherwise use it.
Again, as an emergency measure, he dropped the index on module_id
in order to free up a little space and buy enough time to do a
proper move of the database to Aurora.

Devops-of-2018 being more disciplined than me-of-2012, the index
on module_id was removed in 25da206c. The intention was to make it
so that the state of the code would match what was live on edx.org.
But because the composite index was added in an ad hoc way, what
that really meant was that now queries involving module_id were
_only_ indexed by the (module_id, grade, student_id) composite
index that existed only on edx.org and no other Open edX instances.

We didn't realize this issue until months later. @blarghmatey
created an index to re-add the index for module_id:

  https://github.com/edx/edx-platform/pull/20885

The reason why we didn't accept this immediately is because
migrations for this table are very operationally risky and take
days to run. Faking this migration would have put edx.org even
more out of sync with the Open edX repo. Complicating this
somewhat was the fact that some folks still seem to be running a
variant of the inline analytics on their fork.

So in the end, we're going forward with this migration that brings
the code fully into sync with indexes on edx.org and covers the
obscure inline analytics histogram use case, while still covering
the module_id index needed for the fast generation of certain
reports that focus on a single problem.

Sorry folks.

Fix button/title text

1) Account activation email.
2) Password reset email.
3) Password reset success.

VAN-272

Pin diff-cover to fix tests on Ubuntu 20.04

In commit 9b37e7d0, the logic of
`streak_celebration_is_active` was accidentally
changed such that it no longer checks the
Progress Milestones waffle flag.
This commit fixes that.

Note: This also adds in a transitive check to
`courseware_mfe_is_active`,
which makes sense for Streak Celebration
and should not have any functional impact.

Updated drag and drop version

* Adds the backfill_course_outlines management command to contentstore
* Adds a read-only Django admin interface to learning_sequences for the
  support team and debugging.
* Adds two new functions to the learning_sequences public API:
  key_supports_outlines and get_course_keys_with_outlines

The learning_sequences app isn't supposed to know about contentstore or
modulestore, as it's intended to be extracted out of edx-platform in the
long term. Therefore, the backfill_course_outlines command is in
contentstore, and not learning_sequences.

This work was tracked in TNL-7983, but it also fixes a bug where we were
trying to generate course outlines for libraries (TNL-7981).

All Open edX instances upgrading to Lilac should run the
backfill_course_outlines command as part of their upgrade process.

We weren't properly catching the CourseOutlineData.DoesNotExist error
before this commit. TNL-7979

BOM-2352: Removed unused imports from lms/djangoapps/{grades, instruc…

Run Pyupgrade on edxmako.

BOM-2375-student-part1

BOM-2352: Removed unused imports from lms/djangoapps/{instructor_anal…

fix override error message

ran pyupgrade on course_Wiki, coursewarehistoryextended

[AA-461] Change course metadata export to be a celery task

Centralize the logic for choosing between
MFE and Legacy-frontend courseware within
three new functions:
* courseware_mfe_is_active
* courseware_mfe_is_visible
* courseware_legacy_is_visible

This allows us to create another new function:
* get_courseware_url
which can be called anywhere in LMS/Studio
to get the canonical URL to courseware
content (whether it be MFE or Legacy).

In future commits we we begin using
get_courseware_url throughout the platform.

TNL-7796

feat: Changed username max_length to the specified by django

The terraform policy for the export is already attached to the worker role
AA-461

feat: Upgrade edx-enterprise to 3.17.48 | Adds a mgmt command to update all SystemWideEnterpriseUserRoleAssignment records in a way that makes them more explicitly defined.  ENT-4099.

The setting overrides should've been cleaned up in a previous
commit, but I missed them. This change is a no-op.

Upgrade edx-proctoring to 3.7.8