Query result grouping depends on presence of grouped-by fields in selected set.

[islamaliev]

The following test passes:

func TestQueryOneToMany_WithOnlyAggregatesSelected_ShouldGroupResults(t *testing.T) {
	test := testUtils.TestCase{
		Actions: []any{
			testUtils.CreateDoc{
				CollectionID: 1,
				Doc: `{
					"name": "John Grisham",
					"age": 65,
					"verified": true
				}`,
			},
			testUtils.CreateDoc{
				CollectionID: 1,
				Doc: `{
					"name": "Cornelia Funke",
					"age": 62,
					"verified": false
				}`,
			},
			testUtils.CreateDoc{
				CollectionID: 0,
				DocMap: map[string]any{
					"name":      "Painted House",
					"rating":    4.9,
					"author_id": testUtils.NewDocIndex(1, 0),
				},
			},
			testUtils.CreateDoc{
				CollectionID: 0,
				DocMap: map[string]any{
					"name":      "A Time for Mercy",
					"rating":    4.5,
					"author_id": testUtils.NewDocIndex(1, 0),
				},
			},
			testUtils.CreateDoc{
				CollectionID: 0,
				DocMap: map[string]any{
					"name":      "Theif Lord",
					"rating":    4.8,
					"author_id": testUtils.NewDocIndex(1, 1),
				},
			},
			testUtils.Request{
				Request: `query {
				Book(groupBy: [author]) 
					{
						_avg(_group: { field: rating })
					}
				}`,
				Results: map[string]any{
					"Book": []map[string]any{
						{
							"_avg": 4.733333333333333,
						},
					},
				},
			},
			testUtils.Request{
				Request: `query {
				Book(groupBy: [author]) 
					{
						author {
							name
						}
						_avg(_group: { field: rating })
					}
				}`,
				Results: map[string]any{
					"Book": []map[string]any{
						{
							"author": map[string]any{
								"name": "John Grisham",
							},
							"_avg": 4.7,
						},
						{
							"author": map[string]any{
								"name": "Cornelia Funke",
							},
							"_avg": 4.8,
						},
					},
				},
			},
		},
	}

	executeTestCase(t, test)
}

But the first query (without author { name} in selected fields) should produce the same result as the second one.