Use function getConcordanceTarget() over direct array access

interfaces/MDImporterConcordanceListInterface.php

@@ -0,0 +1,21 @@
+<?PHP
+/**
+ * Describes a concordance list for importer concordance lists.
+ *
+ * @author Joshua Ramon Enslin <joshua@museum-digital.de>
+ */
+declare(strict_types = 1);
+
+/**
+ * Describes a concordance list for importer concordance lists.
+ */
+interface MDImporterConcordanceListInterface {
+    /**
+     * Require a function for getting the concordance target.
+     *
+     * @param string $input Input string.
+     *
+     * @return mixed
+     */
+    public static function getConcordanceTarget(string $input);
+}