Add GROUP BY to graphql cql-first

[polandll]

@DisplayName("Should execute query with groupBy")
public void groupBy(@TestKeyspace CqlIdentifier keyspaceId) {
Map<String, Object> response =
CLIENT.executeDmlQuery(
keyspaceId,
"{ readings(value: {id: 1}, groupBy: {month: true, year: true}) { "
+ "values { "
+ " id"
+ " year "
+ " month "
+ " totalValue: _decimal_function(name: "sum", args: ["value"]) } }"
+ "}");