group size distribution test

ansible/roles/mongodb_query_exporter/templates/values.yml.j2

@@ -1184,3 +1184,45 @@ aggregations:
           }
         }
       ]
+
+
+  - database: {{ mongodb_query_exporter_mongodb_sc_db_name }}
+    collection: groups
+    metrics:
+    - name: sc_groups_size_distribution_by_type
+      type: gauge
+      help: 'Group user size distribution by type'
+      value: count
+      overrideEmpty: true
+      emptyValue: 0
+      labels:
+        - type
+      constLabels:
+        longterm: 'true'
+    mode: pull
+    pipeline: |
+      [
+        {
+          "$project": {
+            "type": 1,
+            "group_size": { "$size": "$users" }
+          }
+        },
+        {
+          "$group": {
+            "_id": { "type": "$type", "group_size": "$group_size" },
+            "count": { "$sum": 1 }
+          }
+        },
+        {
+          "$project": {
+            "_id": 0,
+            "type": "$_id.type",
+            "group_size": "$_id.group_size",
+            "count": { "$toDouble": "$count" }
+        }
+        },
+        {
+          "$sort": { "type": 1, "group_size": 1 }
+        }
+      ]