Collect unmapped entries in dry-run mode

See museum-digital/importer#235

src/MDConcCertainty.php

@@ -56,7 +56,8 @@ final class MDConcCertainty implements MDImporterConcordanceListInterface {
     public static function getConcordanceTarget(string $input):bool {
 
         if (!isset(self::MAPPING[$input])) {
-            throw MDImporterMissingConcordance::setup("certainty identifier", $input);
+            MDImporterMissingConcordance::throw("certainty identifier", $input);
+            return true; // Return default in dry-run mode
         }
 
         return self::MAPPING[$input];