tl;dr: ./occ nextant:index is (a lot) better now.
The whole process of extracting document, indexing them and updating data relative to the original files has been completly reworked. The main result is that you can restart the indexation of your files from the point you stopped/crashed.
Also, fixed few bugs.
Note: as usual, after an upgrade or an installation, you need to index the files from your cloud. First, check that your Solr core has the correct schema by using ./occ nextant:check, then run the indexation: ./occ nextant:index.