Update jsonld to rdf

[francescalb]

Description

Currently saving an invalid jsonld to the triplestore does not raise an error
if the jsonld is invalid ( at least if expected IRIs are just literals).
It just passes, there are no warnings, but also nothing is adde to the triplestore.

This needs to be corrected. Question is how?

with rdflib we can parse the graph and add a base (namespace) to the
generated graph and then check if this generated graph contains irs with that namespace
afterwards.

The what do we want to do? Should this be done somewhere different?

Or shold we reeanblae validation.

Type of change

• Bug fix and code cleanup
• New feature
• Documentation update
• Testing

Checklist for the reviewer

This checklist should be used as a help for the reviewer.

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?
• Is the code properly tested?