* refactor: rename CourseHomeSerializer to StudioHomeSerializer
to better reflect how this serializer/API is used in the Authoring MFE
* feat: adds waffle flags for legacy libraries v1 and new libraries v2 in new Studio Home
These waffle flags replace the MFE env flag LIBRARY_MODE.
* refactor: use contentstore.toggles.libraries_v1_enabled()
and ENABLE_CONTENT_LIBRARIES feature toggle where possible.
ENABLE_CONTENT_LIBRARIES has been incorporated into both the
libraries_v1_enabled() and libraries_v2_enabled() toggles:
FEATURES['ENABLE_CONTENT_LIBRARIES'] must be true for either version of
libraries to be "enabled".