Detect metadata format errors reported by InvenioRDM

[mhucka]

Currently, if any metadata format errors are reported by InvenioRDM for the metadata record sent to it, those errors are not bubbled up and are only visible in the verbose or debug output. The rationale was that IGA should never produce an invalid metadata record in the first place, but the reality is that the IGA test suite is not complete and it's unknown whether it will produce invalid metadata for some inputs. Worse, if the user supplies a metadata record via --read-metadata, that record (which might not have been produced by IGA) could very well have errors.