4.2.0

Added

• Models: Add Edx teams-related events support
• Models: Add Edx notes events support
• Models: Add Edx certificate events support
• Models: Add Edx bookmark (renamed Course Resource) events support
• Models: Add Edx poll and survey events support
• Models: Add Edx Course Content Completion events support
• Models: Add Edx drag and drop events support
• Models: Add Edx cohort events support
• Models: Add Edx content library interaction events support
• Backends: Add ralph.backends.data and ralph.backends.lrs entry points
  to discover backends from plugins.

Changed

• Backends: the first argument of the get_backends method now requires a list
  of EntryPoints, each pointing to a backend class, instead of a tuple of
  packages containing backends.
• API: The RUNSERVER_BACKEND configuration value is no longer validated to
  point to an existing backend.

Fixed

• LRS: Fix querying on activity when LRS contains statements with an object
  lacking a objectType attribute