Refactoring: Use format with named variables

Adding a reviews page to the course and updating the reviews module on the course about page. Removed the existing coursetalk implementation and put it in a fragment, removed the tests as well. Added configuration settings to specify the reviews template as well as the reviews provider. This is all protected by a waffle flag.

PSA was monolothic, now split, with new features, like
a DB-backed partial pipeline. FB OAuth2 version also upped.

Partial pipelines don't get cleared except when necessary.
They persist for special cases like change of browser while
still mid-pipeline (i.e. email validation step).

Refactor, cleanup, and update of a lot of small things as well.

PLEASE NOTE the new `social_auth_partial` table.

LEARNER-1341

- Keeps platform set default of "Audit" to be backwards compatible and not break stuff
- get COURSE_MODE_DEFAULTS from config if set

move tasks into tasks.py

add more logging

Defaults to SUPPORT_SITE_LINK intentionally.
Also fixed surrounding quality tests, and overall
quality improvements.

This reverts commit f97f0525, reversing
changes made to 800bcd8e.

This also serves as a slight refactor of ENT-392.

Pulling URLs from settings allows us to rely on site configuration overrides in order to support multi-tenancy.

LEARNER-1103

Add Enterprise sidebar to login and registration views; remove unneeded fields; make registration form more narrow

The read_cached_programs switch was used to control the release of changes for reading programs exclusively from the cache. With those changes stable, the switch is no longer necessary.

LEARNER-382

* Reorders form fields, and updates labels, placeholders, and tip text
* Increases clickable area for links and labels.
* Removes "*" markers from required fields, and instead adds
  "(optional)" labels to visible optional fields.
* Updates font colors and sizes, and removes box shadows
* Adds custom drop-down styles
* Improves responsive design scaling for small screens
* Make Terms of Service and Honor Code open in new window to avoid losing form
  field values.

This makes it possible to refer to multiple book from a single app.

This also means that Open edX branches will be able to pass bok-choy
tests (at least if the books have already been built.)

This reverts commit 65f13dde.

This reverts commit 88dd85ca, reversing
changes made to bf8aef33.

Although we are phasing out our support of OIDC, this particular feature will allow us to eliminate many of the settings we
share across services. Instead of reading various endpoints and secret keys from settings or hardcoded values, services
with the proper authentication backend can simply read (and cache) the information from this endpoint.

ECOM-3629