implemented hiding/unhiding of mailing lists on the database side

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

@@ -80,6 +80,20 @@ public class Database {
                 var marks = String.join(", ",arr);
                 sb.append("(").append(marks).append(")");
             }
+            if (!where.isEmpty()){
+                var clauses = new ArrayList<String>();
+                sb.append(" WHERE ");
+
+                for (var entry : where.entrySet()){
+                    var arr = new String[entry.getValue().size()];
+                    Arrays.fill(arr,"?");
+                    var marks = String.join(", ",arr);
+                    clauses.add("("+entry.getKey()+" IN ("+marks+"))");
+                    args.addAll(entry.getValue());
+                }
+                sb.append(String.join(" AND ",clauses));
+
+            }
             var sql = sb.toString();
             LOG.debug(sql);
             try {