https://github.com/edx/edx-platform/pull/20645
This introduces:
* A new XBlock runtime that can read and write XBlocks that are persisted using
Blockstore instead of Modulestore. The new runtime is currently isolated so
that it can be tested without risk to the current courseware/runtime.
* Content Libraries v2, which store XBlocks in Blockstore not modulestore
* An API Client for Blockstore
* "Learning Context" plugin API. A learning context is a more abstract concept
than a course; it's a collection of XBlocks that serves some learning purpose.
