The import logic was inconsistent and hard to extend. The new
approach facilitates a parser to walk the incoming JSON-LD structure,
apply entity mapping for each construct and results in an
abstract array that is almost ready to be handed over to DataHandler.

A wrapper will look up existing records for relating to the imported
data. At last the resulting array is handed over to DataHandler
to process.

@@ -0,0 +254,4 @@
+    private function wasUpdatedRecently(string $table, int $uid, int $threshold): bool
+    {
+        $queryBuilder = $this->connectionPool->getQueryBuilderForTable($table);
+        $queryBuilder->getRestrictions()->removeAll();