Show 100000+ in stats when there are more than 100000 alert groups in the result (#1901)

# What this PR does

## Which issue(s) this PR fixes

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - Change permissions used during setup to better represent actions being taken by @mderynck ([#2242](https://github.com/grafana/oncall/pull/2242))
+- Display 100000+ in stats when there are more than 100000 alert groups in the result ([#1901](https://github.com/grafana/oncall/pull/1901))
 
 ## v1.3.1 (2023-06-26)
 

engine/apps/api/views/alert_group.py

@@ -400,20 +400,13 @@ class AlertGroupView(
 
     @action(detail=False)
     def stats(self, *args, **kwargs):
-        alert_groups = self.filter_queryset(self.get_queryset())
-        # Only count field is used, other fields left just in case for the backward compatibility
+        MAX_COUNT = 100001
+        alert_groups = self.filter_queryset(self.get_queryset())[:MAX_COUNT]
+        count = alert_groups.count()
+        count = f"{MAX_COUNT-1}+" if count == MAX_COUNT else str(count)
         return Response(
             {
-                "count": alert_groups.filter().count(),
-                "count_previous_same_period": 0,
-                "alert_group_rate_to_previous_same_period": 1,
-                "count_escalations": 0,
-                "count_escalations_previous_same_period": 0,
-                "escalation_rate_to_previous_same_period": 1,
-                "average_response_time": None,
-                "average_response_time_to_previous_same_period": None,
-                "average_response_time_rate_to_previous_same_period": 0,
-                "prev_period_in_days": 1,
+                "count": count,
             }
         )