implemented hiding/unhiding of mailing lists on the database side

src/main/java/de/srsoftware/widerhall/data/ListMember.java

@@ -43,7 +43,7 @@ public class ListMember {
         Database.open().query(sql.toString()).run();
     }
 
-    public static List<String> listsOf(User user) {
+    public static List<String> listsOwnedBy(User user) {
         var list = new ArrayList<String>();
         try {
             var rs = Database.open()