Given an iterator of dicts, merge them losing no information.
*dicts – arguments are all supposed to be dict to merge into one
dict merged without losing information
Normalize date fields as expected by swh workers.
If date is a list, elect arbitrarily the first element of that list
If date is (then) a string, parse it through dateutil.parser.parse to extract a datetime.
Then normalize it through swh.model.identifiers.normalize_timestamp.
The swh date object