New `aggregate` object

query {
  aggregate(query: {
    from: { type: TABLE, id: 1234567890 },
    group_by: [{ column_id: "task_owner", limit: 10 }],
    limit: 2,
    query: {
      rules: [{
        operator: any_of,
        column_id: "status",
        compare_value: "done_labels"
      }]
    },
    select: [
      {
        type: FUNCTION,
        function: {
          function: SUM,
          params: [{ type: COLUMN, column: { column_id: "task_estimation" } }]
        },
        as: "sum"
      },
      {
        type: COLUMN,
        column: { column_id: "task_owner" },
        as: "task_owner"
      }
    ]
  }) {
    results {
      entries {
        alias
        value {
          ... on AggregateGroupByResult { value_string }
          ... on AggregateBasicAggregationResult { result }
        }
      }
    }
  }
}