MM-43084 update product limits through webhook and websocket (#20076)

* Define interfaces for updating subscriptions and product limits from CWS webhook.

plugin/hooks.go

@@ -42,6 +42,7 @@ const (
 	RunDataRetentionID              = 24
 	OnInstallID                     = 25
 	OnSendDailyTelemetryID          = 26
+	OnCloudLimitsUpdatedID          = 27
 	TotalHooksID                    = iota
 )
 
@@ -264,4 +265,9 @@ type Hooks interface {
 	//
 	// Minimum server version: 6.5
 	OnSendDailyTelemetry()
+
+	// OnCloudLimitsUpdated is invoked product limits change, for example when plan tiers change
+	//
+	// Minimum server version: 7.0
+	OnCloudLimitsUpdated(limits *model.ProductLimits)
 }