These changes unify four different approaches to JWT creation, moving the core of the AccessTokenView to a general-purpose JwtBuilder class. This utility class defaults to using the system's JWT configuration, but it will allow overriding of the signing key and audience claim to support those clients which still require this. Part of ECOM-4566.

Replaces settings value.
TNL-4669

When releasing the versioned assets work, we stumbled on a problem with old pickled
versions of the StaticContent objects residing in cache, which triggered a bug in the
code. Not wanting to blow away all cached items, we ended up having to revert and add
in some backwards-compatible helper code to ease the transition.

With this, we'll now utilize the version argument that Django's caching interface
allows, in conjunction with a constant value that can be modified when breaking changes
are being made, to let us gracefully ignore older cached course assets.

* Renames discussion_module to discussion_xblock
* Moves common/lib/xmodule/xmodule_discussion to openedx/core/lib/xblock_builtin/xblock_discussion

This reverts commit 9967b6fd.

We're seeing errors in NR from objects read out of the cache lacking the
'StaticContent' object has no attribute 'content_digest'
File "/edx/app/edxapp/edx-platform/common/djangoapps/contentserver/middleware.py",
    line 70, in process_request

This reverts commit 849ebc5f.

This commit "undoes"a previous hotfix, and allows a cms course_publish
signal to trigger a block_structure update_course_in_cache task, which
is run on an lms worker queue.

Changes:
    -exposes ALTERNATE_QUEUE_ENVS
    -adds routing layer in celery.py
    -moves prior dev_with_worker settings file to devstack_with_worker
    -moves course_block api functionality into openedx/core/djangoapps/content/block_structure

Added duplicate video failed status for VAL.

This moves the functionality of the 'export_course'  management command from lms/djangoapps/courseware
over to the Studio codebase.  This reflects its use going forward to be run with cms settings, to
export the content of the Studio modulestore instead of the LMS modulestore.  The management
command is used by an analytics workflow to output course content for researchers.

set max_num_courses_in_cache on modulestore

TNL-4484

By default, disable all caching in tests, to preserve test independence.
In order to enable caching, inherit from CacheSetupMixin, and specify
which cache configuration is needed.

[EV-32]

Instead, use a class attribute to define test behavior. This allows for
easier addition of new mixins over time.

TNL-4366
Changes in studio to allow the hide_after_due setting to be utilized.

Includes:
    -python changes to contentstore, where the data is stored.
    -refactoring of timed-examination-preference-editor.underscore, to add this
        setting and make the editor more accessible.
    -javascript changes to link the new setting to the correct data model.
    -sass updates to fix a11y issues on the editor modal.
    -addition of post-due visibility information to course outline in studio.
    -new tests: python, js, acceptance, and a11y

Revert "SUST-35 Implementation of course_key_from_string_or_404 to return course_key or raise a 404"

[PERF-303] Integer XBlocks/XModules into the static asset pipeline.

This PR, based on hackathon work from Christina/Andy, implements a way to discover all installed XBlocks and XModules and to enumerate their public assets, then pulling them in during the collectstatic phase and hashing them.  In turn, the methods for generating URLs to resources will then returned the hashed name for assets, allowing them to be served from nginx/CDNs, and cached heavily.

TNL-4366
Changes in studio to allow the hide_after_due setting to be utilized.

Includes:
    -python changes to contentstore, where the data is stored.
    -refactoring of timed-examination-preference-editor.underscore, to add this
        setting and make the editor more accessible.
    -javascript changes to link the new setting to the correct data model.
    -sass updates to fix a11y issues on the editor modal.
    -addition of post-due visibility information to course outline in studio.
    -new tests: python, js, acceptance, and a11y

Revert "SUST-35 Implementation of course_key_from_string_or_404 to return course_key or raise a 404"