datastreams: better exception handling

[slint]

Readers/transformers/writers can have unexpected errors, e.g. because of malformed data or missed edge cases. We should probably have a more "forgiving" strategy that allows not completely failing on generic errors, but still preserving any context-aware or useful errors that could help with debugging/fixing the input data.

Example:

This line is quite error prone if something is malformed, makes me wonder if we should have a global try/except so the datastream.process() wouldnt fail 🤔

Originally posted by @ppanero in #167 (comment)

[ppanero]

Required for Zenodo migration:

Some grants failed to be processed by the datastreams code. We need to add error logging logic to find these and address separately (in invenio-vocabularies)

might be related to #221