sprockets/src/main/java/net/sf/sprockets/net/Uris.java
public static Uri groupBy(Uri uri, String groupBy) {
        return groupByHavingLimit(uri, groupBy, null, null);
    }
public static Uri groupBy(Uri uri, String groupBy) {
        return groupByHavingLimit(uri, groupBy, null, null);
    }
Append a {@link Content#GROUP_BY group_by} query parameter to the URI.

@since 2.4.0