[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/gtsmodel/webpushsubscription.go

@@ -0,0 +1,82 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package gtsmodel
+
+// WebPushSubscription represents an access token's Web Push subscription.
+// There can be at most one per access token.
+type WebPushSubscription struct {
+	// ID of this subscription in the database.
+	ID string `bun:"type:CHAR(26),pk,nullzero"`
+
+	// AccountID of the local account that created this subscription.
+	AccountID string `bun:"type:CHAR(26),nullzero,notnull"`
+
+	// TokenID is the ID of the associated access token.
+	// There can be at most one subscription for any given access token,
+	TokenID string `bun:"type:CHAR(26),nullzero,notnull,unique"`
+
+	// Endpoint is the URL receiving Web Push notifications for this subscription.
+	Endpoint string `bun:",nullzero,notnull"`
+
+	// Auth is a Base64-encoded authentication secret.
+	Auth string `bun:",nullzero,notnull"`
+
+	// P256dh is a Base64-encoded Diffie-Hellman public key on the P-256 elliptic curve.
+	P256dh string `bun:",nullzero,notnull"`
+
+	// NotificationFlags controls which notifications are delivered to a given subscription.
+	// Corresponds to model.PushSubscriptionAlerts.
+	NotificationFlags WebPushSubscriptionNotificationFlags `bun:",notnull"`
+}
+
+// WebPushSubscriptionNotificationFlags is a bitfield representation of a set of NotificationType.
+type WebPushSubscriptionNotificationFlags int64
+
+// WebPushSubscriptionNotificationFlagsFromSlice packs a slice of NotificationType into a WebPushSubscriptionNotificationFlags.
+func WebPushSubscriptionNotificationFlagsFromSlice(notificationTypes []NotificationType) WebPushSubscriptionNotificationFlags {
+	var n WebPushSubscriptionNotificationFlags
+	for _, notificationType := range notificationTypes {
+		n.Set(notificationType, true)
+	}
+	return n
+}
+
+// ToSlice unpacks a WebPushSubscriptionNotificationFlags into a slice of NotificationType.
+func (n *WebPushSubscriptionNotificationFlags) ToSlice() []NotificationType {
+	notificationTypes := make([]NotificationType, 0, NotificationTypeNumValues)
+	for notificationType := NotificationUnknown; notificationType < NotificationTypeNumValues; notificationType++ {
+		if n.Get(notificationType) {
+			notificationTypes = append(notificationTypes, notificationType)
+		}
+	}
+	return notificationTypes
+}
+
+// Get tests to see if a given NotificationType is included in this set of flags.
+func (n *WebPushSubscriptionNotificationFlags) Get(notificationType NotificationType) bool {
+	return *n&(1<<notificationType) != 0
+}
+
+// Set adds or removes a given NotificationType to or from this set of flags.
+func (n *WebPushSubscriptionNotificationFlags) Set(notificationType NotificationType, value bool) {
+	if value {
+		*n |= 1 << notificationType
+	} else {
+		*n &= ^(1 << notificationType)
+	}
+}