#9 - Added records.published_date column, extracted from the "dc:date" and updated the code to use it (instead of the records.date, now renamed to update_date) when consolidating the count_spans.
- Added one more check to the endpoint merging strategy: if the contexts share the same name and ISSN the other checks are skipped
- Replaced the mass insert query builder and the transaction retrial by their Laravel counterparts
- Added ISSN validation