directly implement the models instead of inheriting from kolibri
directly implement the models instead of inheriting from kolibri

jayoshih/content-curation,jayoshih/content-curation,jayoshih/content-curation,aronasorman/content-curation,fle-internal/content-curation,DXCanas/content-curation,jayoshih/content-curation,fle-internal/content-curation,jonboiser/content-curation,aronasorman/content-curation,fle-internal/content-curation,jonboiser/content-curation,fle-internal/content-curation,jonboiser/content-curation,DXCanas/content-curation,DXCanas/content-curation,aronasorman/content-curation,jonboiser/content-curation,DXCanas/content-curation