[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

1 files changed, 85 insertions, 0 deletions

diff --git a/internal/processing/push/push.go b/internal/processing/push/push.go
new file mode 100644
index 000000000..f46280386
--- /dev/null
+++ b/internal/processing/push/push.go
@@ -0,0 +1,85 @@
+// 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 push
+
+import (
+	"context"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/state"
+	"github.com/superseriousbusiness/gotosocial/internal/typeutils"
+)
+
+type Processor struct {
+	state     *state.State
+	converter *typeutils.Converter
+}
+
+func New(state *state.State, converter *typeutils.Converter) Processor {
+	return Processor{
+		state:     state,
+		converter: converter,
+	}
+}
+
+// getTokenID returns the token ID for a given access token.
+// Since all push API calls require authentication, this should always be available.
+func (p *Processor) getTokenID(ctx context.Context, accessToken string) (string, gtserror.WithCode) {
+	token, err := p.state.DB.GetTokenByAccess(ctx, accessToken)
+	if err != nil {
+		err := gtserror.Newf("couldn't find token ID for access token: %w", err)
+		return "", gtserror.NewErrorInternalError(err)
+	}
+
+	return token.ID, nil
+}
+
+// apiSubscription is a shortcut to return the API version of the given Web Push subscription,
+// or return an appropriate error if conversion fails.
+func (p *Processor) apiSubscription(ctx context.Context, subscription *gtsmodel.WebPushSubscription) (*apimodel.WebPushSubscription, gtserror.WithCode) {
+	apiSubscription, err := p.converter.WebPushSubscriptionToAPIWebPushSubscription(ctx, subscription)
+	if err != nil {
+		err := gtserror.Newf("error converting Web Push subscription %s to API representation: %w", subscription.ID, err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	return apiSubscription, nil
+}
+
+// alertsToNotificationFlags turns the alerts section of a push subscription API request into a packed bitfield.
+func alertsToNotificationFlags(alerts *apimodel.WebPushSubscriptionAlerts) gtsmodel.WebPushSubscriptionNotificationFlags {
+	var n gtsmodel.WebPushSubscriptionNotificationFlags
+
+	n.Set(gtsmodel.NotificationFollow, alerts.Follow)
+	n.Set(gtsmodel.NotificationFollowRequest, alerts.FollowRequest)
+	n.Set(gtsmodel.NotificationFavourite, alerts.Favourite)
+	n.Set(gtsmodel.NotificationMention, alerts.Mention)
+	n.Set(gtsmodel.NotificationReblog, alerts.Reblog)
+	n.Set(gtsmodel.NotificationPoll, alerts.Poll)
+	n.Set(gtsmodel.NotificationStatus, alerts.Status)
+	n.Set(gtsmodel.NotificationUpdate, alerts.Update)
+	n.Set(gtsmodel.NotificationAdminSignup, alerts.AdminSignup)
+	n.Set(gtsmodel.NotificationAdminReport, alerts.AdminReport)
+	n.Set(gtsmodel.NotificationPendingFave, alerts.PendingFavourite)
+	n.Set(gtsmodel.NotificationPendingReply, alerts.PendingReply)
+	n.Set(gtsmodel.NotificationPendingReblog, alerts.PendingReblog)
+
+	return n
+}