- sharing enabled for custom URLs only if URL actually specified

xblock-external-ui: Include CSRF token in the API answer
xblock-external-ui: Include full path when building local_url
xblock-external-ui: Fix TestHandleXBlockCallback & bok_choy, add tests
xblock-external-ui: Only return `instance` in `_invoke_xblock_handler()`
xblock-external-ui: Group resources by hash tag to avoid duplicate loads
xblock-external-ui: PEP8
xblock-external-ui: Fail early if the XBlock view is called anonymously

    We used to serve anonymous requests, but most XBlocks assume that the
    user is logged in, which can generate a lot of errors when the user is
    accessed or when an XBlock ajax callback is queried. Fail early to only
    get one error per page load, and prevent displaying the XBlock
    altogether when the LMS doesn't find an active user session.

xblock-external-ui: Add request params in view render context
xblock-external-ui: HTTP error status when file is too large for handler
xblock-external-ui: Fix unicode encodings in XBlock rendering
xblock-external-ui: Feature flag for API call ENABLE_XBLOCK_VIEW_ENDPOINT

Removes old payment and verification endpoints, views, templates, and tests, making the new split flow the default. The SEPARATE_VERIFICATION_FROM_PAYMENT feature flag is also removed.

Adds mode creation endpoint to course_modes app and ability to bypass media device access prompt when proceeding through verification flow in a testing environment.

Added bokchoy tests and assets (csv files) for CSV auto reg and enrollment.
Set the env flag "ALLOW_AUTOMATED_SIGNUPS": true in bok_choy.env.json

Resolved quality issues.

resolved cherry pick conflicts

Improved bokchoy tests as per code review suggestions.

added the BDD in the docstrings for all the test scenarios

changed the bok choy test string

Improved bokchoy tests as per further code review suggestions.

Made a MembershipPageAutoEnrollSection a separate PageObject.

Including:

* Change path for mongo_metadata_inheritance to use unique temp dir
* Update SASS_CACHE_PATH with thread-safe temp dir
* Remove hard coded directory reference for grades download tests
* Remove hard coded directory reference for direct mongo test

Update db cache