feat(backend/data_package): prevent a package from getting transferred using...

feat(backend/data_package): prevent a package from getting transferred using sett if it has been transferred before

When transferring a data package using sett, the [check endpoint will be called](https://gitlab.com/biomedit/sett/-/blob/eda60c5fdb5a934b76e883dbbb73b553eb89234a/sett/core/portal_api.py

).
Previously, it was possible to transfer the same data package more than once.
Now the check endpoint will return a validation error when a data package with the same metadata as in an existing data package is used.

Closes #350

Signed-off-by: martinfrancois <f.martin@fastmail.com>