Add error checks for folder related backend operations

[otahontas]

Proposed solution

Currently results from folder-related backend operations are not checked, so if backend is not running / request fails, wizard will just continue and crash later.

Following situations are problematic currently:

• Addition of folders: if posting to backend fails, wizard continues to second step
• Addition of objects to folders: if adding to folder fails in backend, nothing is reported (however folder isn't added to redux store in frontend, which is good). As a result, object is in backend, but not connected to folder
• Deletion of folder: if deleting folder or objects inside it fails, nothing is reported (also folder is not removed from store at all if any of requests to backend fails).

We should handle error checks for backend operations and report fails to user + in best situation these.

DoD (Definition of Done)

Errors are checked and handled accordingly, user is notified