Use Redis for sessions and fix STATIC_ROOT_BASE

🐛(config) reintroduce the STATIC_ROOT_BASE setting

We thought this setting was useless but it is used in 1 place in edx-platform:
edx-platform/common/djangoapps/pipeline_mako/helpers/studiofrontend.py
sigh.

Fix logging environment in Sentry

🐛(sentry) fix logging environment in Sentry

The previous implementation was not working because the
ENVIRONMENT setting was redefined after the LOGGING
setting had already been set to with "production" as
the environment. I propose to directly override the
value of the environment in the LOGGING setting.

Upgrade edx-platform (oee flavor) to hawthorn.1-1.0.0-rc.1

Upgrade to the first release candidate of our configurable LTI XBlock.

Improve Sentry configuration

We added environment and release information to our Sentry logs.

Upgrade edx-platform dependency to oee/hawthorn.1-0.1.3

⬆️(edx-platform) upgrade to oee/hawthorn.1-0.1.3

Upgrade edx-platform (oee flavor) to the latest release including a fix
for the configurable LTI consumer xblock.

First releast of Open edX extended

Add a configurable LTI consumer xblock.

Add local node binaries to the path

⚡️(env) add local node binaries to the path

Instead of adding local node binaries to the path only for the
development target, we've decided to make it available for each
edxapp-derived targets. This will ease the later use of paver.

Refactor Dockerfile with multi-stage build and fix the development environment

The development environment was not working properly since we upgraded to hawthorn because assets are built differently in production and in development.

This release fixed the develoment anvironment and comes with a complete rewrite of the Dockerfile to leverage multi-stage builds.

We identified a lot more improvements that could not be done because of design issues in Open edX. For example:

• get rid of the "node_modules" directory in the production image,
• avoid reinstalling everything after mounting sources as volumes in the development image.

We did not surrender on these improvements but will need to spend some time demonstrating what is wrong to edX and submitting Pull Requests' to fix the issues at their root.

Fix EMAIL_BACKEND default

This is a follow-up of 766fcd8, as config requires a "default" keyword.

Improve flexibility of database related settings and bug fixes

The database related settings (mysql & mongodb) were set in one big dictionary variable containing all the parameters:

• some are secret like passwords and some aren't,
• some change at each deployment like host names and some never change.

In Arnold, credentials are stored as OpenShift secrets and injected as environment variables whereas non secret settings are injected from a yaml file. For this reason, we needed to be able to set each database setting separately.

This Release also includes a number of bug fixes:

• update the demo course to hawthorn.1 to match the version of edxapp that we are running,
• fix platform name and description default values to avoid deserialization bug in Open edX while waiting for a fix on edx-platform,
• set a default configuration for password complexity so that automatic creation of users with "/auto_auth" works by default in development,
• add vim editor to development container.