[Libraries] [Collections] [Backend] REST CRUD API for Collections in v2 Libraries

[bradenmacdonald]

1. Define new CRUD REST API to be able to query/manipulate the instances of the newly created Collection Model ([Libraries] [Collections] [Backend] Collections model in Learning Core #225).
   • Don't implement "Delete" -- just raise a 405 for now. Will be handled by [Libraries] [Collections] [Backend] Soft Delete collections #231.
2. These should be defined in edx-platform (in the content_libraries django app) to handle permission checks and interface with the Collection model defined in openedx_learning repo.
   • Similar to how the taxonomy views and apis are implemented.
   • For permissions, use the ContentLibrary associated with the Collection's LearningPackage to determine the user's permissions on the Collection. If the LearningPackage is not associated with a ContentLibrary, raise an error.
3. We also need to emit events when collections are created/edited/updated, which will require adding new event & data types to https://github.com/openedx/openedx-events

[pomegranited]

@bradenmacdonald To clarify: we should use the ContentLibrary associated with the Collection's LearningPackage to determine the user's permissions on the Collection?

[bradenmacdonald]

@pomegranited Yes, exactly. And if the LearningPackage is something other than a content library: throw an error.