Implementation details:
* Anonymous users are assigned a unique ID (like
`anon42c08f9996194e2a9339`) which gets stored in the django session.
`block.scope_ids.user_id` and `block.runtime.anonymous_student_id`
will both return this value.
* User state for anonymous users is stored in the django cache and
automatically expires as the cache gets pruned. Because user state is
stored, anonymous users can use interactive blocks like capa problems.
* There is no mechanism for upgrading to a registered account and
keeping user state since the user state store for anonymous users
(EphemeralKeyValueStore) is completely different than the one for
registered users (DjangoKeyValueStore/"CSM"), and has no "list all
keys" functionality.
* "User State Summary" field values are shared among [recently active]
anonymous users but are not shared with registered users.
* Anonymous users can only access the `public_view` of XBlocks, not the
regular `student_view`.
This commit introduces the changes needed for XBlocks in Blockstore to save
their user state into CSM. Before this commit, all student state for Blockstore
blocks was ephemeral (in-process dict store).
Notes:
* The main risk factor of this PR is that it adds non-course keys to the
course_id field in CSM. If any code (like analytics?) reads course keys
directly out of CSM and doesn't have graceful handling for key types it
doesn't recognize, it could cause an issue. With the included changes to
opaque-keys, calling CourseKey.from_string(...) on these values will raise
InvalidKeyError since they're not CourseKeys. (But calling
LearningContextKey.from_string(...) will work for both course and library
keys.)
* This commit introduces a slight regression for the Studio view of XBlocks in
Blockstore content libraries: their state is now lost from request to request.
I have a follow up PR to give them a proper studio-appropriate state store,
but I want to review it separately so it doesn't hold up this PR and we can
test this PR on its own.
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.
