Implements helper function for serialization

src/main/java/CredentialRepository.java

@@ -138,6 +138,16 @@ public class CredentialRepository implements CredentialRepositoryInterface{
         return this.credentials.size();
     }
 
+    /**
+     * Helper function for serialization
+      * @return
+     */
+
+    private String getWorkingDirectory()
+    {
+        return System.getProperty("user.dir");
+    }
+
 }