Add metrics for mobile versions snapshots (#28191)

* Add metrics for mobile versions snapshots

* Add notifications disabled and fix lint

* Address feedback

* Verify all references to JobTypeActiveUsers

* Fix typos

* Improve platform values

* Add test and MySQL support

server/public/model/session.go

@@ -39,6 +39,13 @@ const (
 //msgp:tuple StringMap
 type StringMap map[string]string
 
+type MobileSessionMetadata struct {
+	Version              string
+	Platform             string
+	Count                float64
+	NotificationDisabled string
+}
+
 // Session contains the user session details.
 // This struct's serializer methods are auto-generated. If a new field is added/removed,
 // please run make gen-serialized.