GitLab

* Removed `model_config` from all models; updated `MyModelSerializer` to include a new `obj_info` field. Updated frontend to take the change into account. (Fixes #78)
* Removed `get_viewset_permissions` from most viewsets and added a generic getter in `MyModelViewset`.
* Added support for composable permissions classes :confetti\_ball: (Fixes #45)
* Cleaned config files: separated the files; added `defaults.yaml`
* Moved `shared` folder (content) to `backend.backend_app.config` (still accessible to frontend, but it's cleaner that way since this folder contains files concerning only the backend).
* Performance update with caching some attributes;
* Even cleaner backend dynamic imports (#46)
* Added a good chunck of documentation related to the backend (#74)
* Added checks (runned when server is started or indirectly with `make check_backend`)

Closes #44

Repo structure complete redesign
Fixes #38

Also removed some stuff