OEOX: Update loep search index after each composedUnit added to oeox

[jh-RLI]

Description of the issue

To finally enable the intended functionality of the oeo-ext plugin view on the OEP we need to update the search index of the LOEP service.

Ideas of solution

The LOEP service runs dbpedia-lookup, a software that is make to create an apache lucene search index based on a RDF file like OWL format. It also allows for triggering the indexing run via a http post request. The OEP must trigger the indexer once a new class was added to the oeox.

Workflow checklist

• I am aware of the workflow in CONTRIBUTING.md