feat: Allow summation of aggregates (sourcenetwork#341)

* Remove previously done todo

* Refactor source collection var

* Refactor source property

* Remove strange variable aliasing

* Refactor isFloat property

* Add summation of aggregates support

* Remove else clause (PR request)

db/tests/query/simple/with_group_count_sum_test.go

@@ -0,0 +1,99 @@
+// Copyright 2022 Democratized Data Foundation
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package simple
+
+import (
+	"testing"
+
+	testUtils "github.com/sourcenetwork/defradb/db/tests"
+)
+
+func TestQuerySimpleWithGroupByStringWithInnerGroupBooleanAndSumOfCount(t *testing.T) {
+	test := testUtils.QueryTestCase{
+		Description: "Simple query with group by string, with child group by boolean, and sum of count",
+		Query: `query {
+					users(groupBy: [Name]) {
+						Name
+						_sum(field: {_group: _count})
+						_group (groupBy: [Verified]){
+							Verified
+							_count(field: _group)
+						}
+					}
+				}`,
+		Docs: map[int][]string{
+			0: {
+				(`{
+				"Name": "John",
+				"Age": 25,
+				"Verified": true
+			}`),
+				(`{
+				"Name": "John",
+				"Age": 32,
+				"Verified": true
+			}`),
+				(`{
+				"Name": "John",
+				"Age": 34,
+				"Verified": false
+			}`),
+				(`{
+				"Name": "Carlo",
+				"Age": 55,
+				"Verified": true
+			}`),
+				(`{
+				"Name": "Alice",
+				"Age": 19,
+				"Verified": false
+			}`)},
+		},
+		Results: []map[string]interface{}{
+			{
+				"Name": "John",
+				"_sum": int64(3),
+				"_group": []map[string]interface{}{
+					{
+						"Verified": true,
+						"_count":   int(2),
+					},
+					{
+						"Verified": false,
+						"_count":   int(1),
+					},
+				},
+			},
+			{
+				"Name": "Alice",
+				"_sum": int64(1),
+				"_group": []map[string]interface{}{
+					{
+						"Verified": false,
+						"_count":   int(1),
+					},
+				},
+			},
+			{
+				"Name": "Carlo",
+				"_sum": int64(1),
+				"_group": []map[string]interface{}{
+					{
+						"Verified": true,
+						"_count":   int(1),
+					},
+				},
+			},
+		},
+	}
+
+	executeTestCase(t, test)
+}