Renforce our metadata extraction process

[syphax-bouazzouni]

Context

During the submission process, we have added a step called "extract_metadata", that do an ad-hoc sparql query to extract each property defined as extracble (with the attribute extractedMetadata: true on it)

And in ncbo/ontologies_linked_data#153, I extracted that code in a mode called MetadataExtractor

Issue

The issue is that it does not always works (see issues below) and is not extracted to a PR for Ontoportal

Related

• Extract metadata process does not work for ontologies that imports other ontolgies ontoportal-lirmm/ontologies_linked_data#57
• Extract "metadata extraction" porcess from the "generate_rdf_file" one ontoportal-lirmm/ontologies_linked_data#59
• Update how the ontology-level attributes are extracted at the process time #293
• export metadata omv:hasOntologyLanguage change to URI #449
• export metadata : prefix missing #448
• Automatic extraction of metadata, new iteration #423
• Metadata vocabulary used : automate the population of this property by looking at the namespace declared inside the source file #421