[feature] Push notifications (#3587)

* Update push subscription API model to be Mastodon 4.0 compatible

* Add webpush-go dependency

# Conflicts:
#	go.sum

* Single-row table for storing instance's VAPID key pair

* Generate VAPID key pair during startup

* Add VAPID public key to instance info API

* Return VAPID public key when registering an app

* Store Web Push subscriptions in DB

* Add Web Push sender (similar to email sender)

* Add no-op push senders to most processor tests

* Test Web Push notifications from workers

* Delete Web Push subscriptions when account is deleted

* Implement push subscription API

* Linter fixes

* Update Swagger

* Fix enum to int migration

* Fix GetVAPIDKeyPair

* Create web push subscriptions table with indexes

* Log Web Push server error messages

* Send instance URL as Web Push JWT subject

* Accept any 2xx code as a success

* Fix malformed VAPID sub claim

* Use packed notification flags

* Remove unused date columns

* Add notification type for update notifications

Not used yet

* Make GetVAPIDKeyPair idempotent

and remove PutVAPIDKeyPair

* Post-rebase fixes

* go mod tidy

* Special-case 400 errors other than 408/429

Most client errors should remove the subscription.

* Improve titles, trim body to reasonable length

* Disallow cleartext HTTP for Web Push servers

* Fix lint

* Remove redundant index on unique column

Also removes redundant unique and notnull tags on ID column since these are implied by pk

* Make realsender.go more readable

* Use Tobi's style for wrapping errors

* Restore treating all 5xx codes as temporary problems

* Always load target account settings

* Stub `policy` and `standard`

* webpush.Sender: take type converter as ctor param

* Move webpush.MockSender and noopSender into testrig

internal/processing/workers/surfacenotify.go

@@ -250,7 +250,7 @@ func (s *Surface) notifyFave(
 	// notify status author
 	// of fave by account.
 	if err := s.Notify(ctx,
-		gtsmodel.NotificationFave,
+		gtsmodel.NotificationFavourite,
 		fave.TargetAccount,
 		fave.Account,
 		fave.StatusID,
@@ -521,7 +521,7 @@ func (s *Surface) notifySignup(ctx context.Context, newUser *gtsmodel.User) erro
 	var errs gtserror.MultiError
 	for _, mod := range modAccounts {
 		if err := s.Notify(ctx,
-			gtsmodel.NotificationSignup,
+			gtsmodel.NotificationAdminSignup,
 			mod,
 			newUser.Account,
 			"",
@@ -647,5 +647,10 @@ func (s *Surface) Notify(
 	}
 	s.Stream.Notify(ctx, targetAccount, apiNotif)
 
+	// Send Web Push notification to the user.
+	if err = s.WebPushSender.Send(ctx, notif, filters, compiledMutes); err != nil {
+		return gtserror.Newf("error sending Web Push notifications: %w", err)
+	}
+
 	return nil
 }