Add a readme for the mobile_api.

An initial breakdown of our areas of the monolith.

Initial README for XModule

Initial README for Track app

Bump to edx-enterprise 1.4.8

Initial README for heartbeat app

INCR-191

Update user_authn README to new format.

Account API: enforce Enterprise policy on backend

INCR-192

INCR-193

Initial README for Discussion

Have a platform-core team that can be responsible for everything that is
not already being owned by a more specific group.

Initial README for Student app

Initial README for the courseware djangoapp.

add LMS endpoint to redirect to identity provider

INCR-120

Right now there are no owners associated but this should clarify what is
considered part of the core and core extensions.  This is not a full
list so things will have to be added as we find that they need an owner
and don't have one.  This list was taken by looking at the parts of our
codebase that is most executed for edx.org and so should represent the
most important things that should probably have owners.

PROD-9: Fix badly performing database query for bulk email by using

updated language list we pull from transifex to support beta languages

INCR-165

Add site configuration check to order history MFE toggle.

INCR-174

Merge pull request #20328 from edx/testeng/bokchoy_auto_cache_update_d6d93178bf4109db7076fddb53b123df530412ae

Bokchoy Testing DB Cache update