Add new fields to GroupType

What does this MR do and why?

This is part of the ongoing Organization work by the grouptenant scale group. Read the blueprint to learn more https://docs.gitlab.com/ee/architecture/blueprints/organization/index.html.

Fields introduced are:

• descendantGroupsCount
• groupMembersCount
• projectsCount

Query plans

1. https://console.postgres.ai/gitlab/gitlab-production-main/sessions/24623/commands/78338

Raw Query

SELECT COUNT(projects) AS "count_projects", "namespaces"."id" AS "namespaces_id"
FROM "namespaces"
         LEFT OUTER JOIN "projects" ON "projects"."archived" != TRUE AND "projects"."namespace_id" = "namespaces"."id"
WHERE "namespaces"."type" = 'Group'
  AND "namespaces"."id" IN
      (1755573, 1761696, 1793858, 1819570, 1920469, 2287432, 2351283, 2452873, 2593421, 2639717, 2750817, 2843837,
       2907304, 3345373, 3455548, 3887963, 3910297, 3925021, 3930213, 3952433)
GROUP BY "namespaces"."id";

2. https://console.postgres.ai/gitlab/gitlab-production-main/sessions/24623/commands/78337

Raw Query

SELECT COUNT(members) AS "count_members", "namespaces"."id" AS "namespaces_id"
FROM "namespaces"
         LEFT OUTER JOIN "members" ON "members"."source_type" = 'Namespace' AND "members"."requested_at" IS NULL AND
                                      "members"."access_level" != 5 AND "members"."source_id" = "namespaces"."id" AND
                                      "members"."type" = 'GroupMember'
WHERE "namespaces"."type" = 'GROUP'
  AND "namespaces"."id" IN
      (1755573, 1761696, 1793858, 1819570, 1920469, 2287432, 2351283, 2452873, 2593421, 2639717, 2750817, 2843837,
       2907304, 3345373, 3455548, 3887963, 3910297, 3925021, 3930213, 3952433)
GROUP BY "namespaces"."id";

3. https://console.postgres.ai/gitlab/gitlab-production-main/sessions/24623/commands/78336

Raw Query

SELECT COUNT(children_namespaces) AS "count_children_namespaces", "namespaces"."id" AS "namespaces_id"
FROM "namespaces"
         LEFT OUTER JOIN "namespaces" "children_namespaces" ON "children_namespaces"."type" = 'Group' AND
                                                               "children_namespaces"."parent_id" = "namespaces"."id"
WHERE "namespaces"."type" = 'Group'
  AND "namespaces"."id" IN
      (1755573, 1761696, 1793858, 1819570, 1920469, 2287432, 2351283, 2452873, 2593421, 2639717, 2750817, 2843837,
       2907304, 3345373, 3455548, 3887963, 3910297, 3925021, 3930213, 3952433)
GROUP BY "namespaces"."id";

How to set up and validate locally

Run the following query on GraphiQL https://gdk.test:3000/-/graphql-explorer:

Query

{
  organization(id: "gid://gitlab/Organizations::Organization/1") {
    id
    path
    groups(sort: NAME_DESC) {
      edges {
        node {
          id
          descendantGroupsCount
          groupMembersCount
          projectsCount
        }
      }
    }
  }
}

Output

{
  "data": {
    "organization": {
      "id": "gid://gitlab/Organizations::Organization/1",
      "path": "default",
      "groups": {
        "edges": [
          {
            "node": {
              "id": "gid://gitlab/Group/35",
              "descendantGroupsCount": 0,
              "groupMembersCount": 5,
              "projectsCount": 2
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/31",
              "descendantGroupsCount": 0,
              "groupMembersCount": 5,
              "projectsCount": 1
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/27",
              "descendantGroupsCount": 0,
              "groupMembersCount": 5,
              "projectsCount": 1
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/24",
              "descendantGroupsCount": 0,
              "groupMembersCount": 4,
              "projectsCount": 2
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/33",
              "descendantGroupsCount": 0,
              "groupMembersCount": 5,
              "projectsCount": 1
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/29",
              "descendantGroupsCount": 0,
              "groupMembersCount": 5,
              "projectsCount": 1
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/109",
              "descendantGroupsCount": 0,
              "groupMembersCount": 1,
              "projectsCount": 0
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/110",
              "descendantGroupsCount": 0,
              "groupMembersCount": 1,
              "projectsCount": 0
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/108",
              "descendantGroupsCount": 1,
              "groupMembersCount": 1,
              "projectsCount": 0
            }
          },
          {
            "node": {
              "id": "gid://gitlab/Group/107",
              "descendantGroupsCount": 2,
              "groupMembersCount": 1,
              "projectsCount": 0
            }
          }
        ]
      }
    }
  }
}

Related to #420702 (closed)

app/models/group.rb

@@ -336,16 +336,7 @@ def descendant_groups_counts
     end
 
     def projects_counts
-      projects_table = Project.arel_table
-      namespaces_table = Namespace.arel_table
-
-      join_on = projects_table[:namespace_id].eq(namespaces_table[:id]).and(projects_table[:archived].not_eq(true))
-      join_clause = namespaces_table
-                      .join(projects_table, Arel::Nodes::OuterJoin)
-                      .on(join_on)
-                      .join_sources
-
-      joins(join_clause).group(:id).count(:projects)
+      left_joins(:non_archived_projects).group(:id).count(:projects)
     end
 
     def group_members_counts