[feature] Implement Web Push notification policy (#3721)

* Web Push: add policy column to subscriptions

* Web Push: add policy to API

* Web Push: test notification policy

* go-fmt unrelated file (how did this get thru?)

testrig/testmodels.go

@@ -3610,6 +3610,7 @@ func NewTestWebPushSubscriptions() map[string]*gtsmodel.WebPushSubscription {
 				gtsmodel.NotificationPendingReply,
 				gtsmodel.NotificationPendingReblog,
 			}),
+			Policy: gtsmodel.WebPushNotificationPolicyFollowed,
 		},
 	}
 }