refs #17408 [master-v5] reactivate resolver sid 48

* added missing method in RecordDriver SolrAI

module/finc/src/finc/RecordDriver/SolrAI.php

@@ -266,6 +266,16 @@ class SolrAI extends SolrDefault implements
         return isset($this->fields['issn']) ? $this->fields['issn'] : [];
     }
 
+    /**
+     * Get an array of all ISSNs associated with the record (may be empty).
+     *
+     * @return array of issns
+     */
+    public function getCleanISSN()
+    {
+        return $this->getAIRecord('rft.issn');
+    }
+
     /**
      * Get the eISSN from a record.
      *