This is primarily to reduce load on MongoDB, where we've lately
had performance problems that we suspect are caused by very
large course structures being evicted from MongoDB's cache. This
may potentially give us a path to better performance as well,
but that's not the goal of this commit.

Surprisingly, LZ4 seemed to actually run more slowly than zlib
for this. Possibly because of some overhead in the Python
bindings? GZip was also surprisingly slow given that it uses
zlib underneath (something like 5x slower).

Use separate cache backend for caching structures.

Abstract out course structure cache.

add datadog metrics for compressed course structure sizes

Since we're using a different cache background, we don't need to have a cache prefix

Use dummy cache backend for tests.

Fallback to default cache if course_structure_cache doesn't exist.

Ensure that is_hidden does not affect equality checks.

Merge release into master

Conflicts:
	cms/djangoapps/contentstore/views/course.py

MIT CCX: Use CCX Keys

Prevent duplication of tabs with different names.

Make addCleanup idempotent.

Update translations (autogenerated message)

only require ccx-keys once

get_current_ccx will now expect a CourseKey instance as its argument, and will raise a value error if this expectation is not met.

document reason for local import

add special methods to pass attribute setting and deletion through to the wrapped modulestore

add __setattr__ and __delattr__ per code review, update __init__ to work with new methods

style change per code review

clean up context manager usage as recommended by code review

remove unused code and imports

convert modulestore type tests to use the `get_modulestore_type` api, remove unused imports

code quality: add docstrings

increase coverage for utils tests

fix bug found in testing.

increase test coverage on modulestore wrapper

code quality fixes

code-quality: ignore import error, but mark site for future consideration

ECOM-1724 a11y footer updates

First draft.

Fix flaky lettuce test. TNL-1452

In bulk_operations() exit, emit signals at the end.

* Add action text to social media links.
* Make the alt text for mobile links more descriptive.

Course Blocks + Navigation API (feature flagged) for Mobile

[LTI Provider] Basic LTI authentication

Avoid POSTing unnecessary payment processor parameter

Release

Sometimes this file does not exist depending on when a test failed. Remove it gracefully.

This is an initial authentication implementation that allows LTI users to
log in transparently to edX. The behavior is driven by pilot users at
Harvard; this was the most requested feature.

The patch creates a new database model that maps users' LTI identifiers
to newly-created edX accounts. If an LTI launch comes in with a user_id
field that is not in the database, a new edX account is created with a
random user name and password. This account is then stored in the
database, so that it is permanently associated with the LTI user ID.

This patch takes a simplistic approach to session management. If a user
is logged in with a different account when they perform an LTI launch,
they will be logged out and then re-logged in using their LTI account.

In order to keep the patch simple, I have split out some refactoring
that needs to be done into a separate branch that I'll post once this
has been merged. Since we no longer redirect to the login page, we don't
need to maintain two separate LTI endpoints (one for the LTI launch and
one for authenticated users), or deal with the session management that
requires. There are also multiple fetches of the LtiConsumer object
(one in the view, one in the signature validation) that the later
patch will consolidate into one.

This branch fixes the previous conflicts with the test refactoring
carried out in PR 8240.

Specified number of mongo and split calls in xblock outline handler test with ddt.

Merge pull request #8495 from edx/shr/bug/tnl-2122-fix-show-enable-import-from-youtube-transcript-button

add name param check_transcripts

Patch/2015 06 11

PLAT-674

show credit eligibility requirements in studio

ECOM-1591

remove references to middleware that were missed previously

use key apis rather than local implementation of key conversion.  remove local implementationa

remove spurious test for attribute

fix test setUp to avoid unneeded flattening

code quality fixes

add security check ensuring that the coach is coach for *this* CCX.

prevent ccx/deprecated course id problems

1.  do not allow ccx objects to be created if the course id is deprecated
2.  filter out any ccx memberships that involve deprecated course ids (in case there are bad ccxs in the database)

Fix test failures and errors arising from incorrect code path execution

Create context manager to handle unwrapping and restoring ccx values for the modulestore wrapper, employ it throughout modulestore wrapper implementation

Implement the use of CCX opaque keys throughout the ccx code base

include the new custom ccx id package in the github checkouts list

update the coach dashboard wrapper to get CCX information from the incoming course_id, if possible

update function signatures for all view functions to expect CCX as passed by the dashboard wrapper (default to None), remove calls to get_ccx_for_coach as the ccx is passed in.

update reverse calls in python view code to use a CCXLocator for the URL instead of a CourseLocator

use CCXLocator where necessary

use course id to find ccx, instead of thread local

remove unused method and related tests

use course id for getting ccx

provide course id to the get_current_ccx method

ensure the course id passed in is a CourseKey instance of some type whether it starts out as a string or not

use the provided block to figure out what the course_id should be, then get the ccx for that

redirect to ccx dashboard using coach ccx if no ccx is passed in

update student dashboard listing for ccx to build an appropriate url from a CCXLocator, not from the course locator.

refactor building the ccx locator so we don't have to do it repeatedly

begin test refactoring after ccx_keys introduction

Ensure that when access checking happens, the course_locator form of a ccx locator is used.  This ensures that the access check happens against the course and it is not necesarry to duplicate the entire access control structure for the course.

pick up api change in ccx-keys

create and conditionally use a wrapper for the mixed modulestore returned by xmodule.modulestore.django.modulestore

the wrapper will strip and restore ccx values from CourseKey and UsageKey objects

fix return values on a few methods

remove unused symbol

pull updated ccx-keys package

set course_id on the caching descriptor system to avoid api incompatibilities in some subsystems

use ccx.course instead of self.course

fix get method to find course keys from blocks that are not themselves keys but have a location attribute (which will be a key)

if an item coming out of the db has children, restore the ccx to them as well

if the block passed in has a CCX key, unwrap that before we try to look up the override, otherwise it will never be found.

pick up a change in the ccx keys package that allows for stripping CCX identity from a usage key

begin writing tests to cover this modulestore wrapper

remove the switch_pocs view, the url pattern for it, and the tests that covered it

remove the ccx context and the middleware responsible for setting the current CCX.  These are no longer needed

all dashboard views should raise 404 if a ccx is not provided by the coach_dashboard decorator

code quality

prevent errors resulting from trying to `get` a ccx based on non-unique criteria.

remove obsolete usage of ACTIVE_CCX_KEY

fix setUp method for grading tests to properly create grades for the ccx rather than for the course.

clean up reverse calls

code quality

adding docstrings to clarify purpose of this patch

fix bug in getting ccx for coach

fix grading views to properly fetch a ccx-ified course so that grades for that version will be calculated

fix small errors in modulestore implementation

fix errant merge marker

update call to get_current_ccx after key refactoring merged with tab changes