[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, 58 insertions, 0 deletions

diff --git a/internal/config/helpers.gen.go b/internal/config/helpers.gen.go
index e1c41638c..fd1b86898 100644
--- a/internal/config/helpers.gen.go
+++ b/internal/config/helpers.gen.go
@@ -4274,6 +4274,64 @@ func GetCacheWebfingerMemRatio() float64 { return global.GetCacheWebfingerMemRat
 // SetCacheWebfingerMemRatio safely sets the value for global configuration 'Cache.WebfingerMemRatio' field
 func SetCacheWebfingerMemRatio(v float64) { global.SetCacheWebfingerMemRatio(v) }
 
+// GetCacheWebPushSubscriptionMemRatio safely fetches the Configuration value for state's 'Cache.WebPushSubscriptionMemRatio' field
+func (st *ConfigState) GetCacheWebPushSubscriptionMemRatio() (v float64) {
+	st.mutex.RLock()
+	v = st.config.Cache.WebPushSubscriptionMemRatio
+	st.mutex.RUnlock()
+	return
+}
+
+// SetCacheWebPushSubscriptionMemRatio safely sets the Configuration value for state's 'Cache.WebPushSubscriptionMemRatio' field
+func (st *ConfigState) SetCacheWebPushSubscriptionMemRatio(v float64) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.Cache.WebPushSubscriptionMemRatio = v
+	st.reloadToViper()
+}
+
+// CacheWebPushSubscriptionMemRatioFlag returns the flag name for the 'Cache.WebPushSubscriptionMemRatio' field
+func CacheWebPushSubscriptionMemRatioFlag() string { return "cache-web-push-subscription-mem-ratio" }
+
+// GetCacheWebPushSubscriptionMemRatio safely fetches the value for global configuration 'Cache.WebPushSubscriptionMemRatio' field
+func GetCacheWebPushSubscriptionMemRatio() float64 {
+	return global.GetCacheWebPushSubscriptionMemRatio()
+}
+
+// SetCacheWebPushSubscriptionMemRatio safely sets the value for global configuration 'Cache.WebPushSubscriptionMemRatio' field
+func SetCacheWebPushSubscriptionMemRatio(v float64) { global.SetCacheWebPushSubscriptionMemRatio(v) }
+
+// GetCacheWebPushSubscriptionIDsMemRatio safely fetches the Configuration value for state's 'Cache.WebPushSubscriptionIDsMemRatio' field
+func (st *ConfigState) GetCacheWebPushSubscriptionIDsMemRatio() (v float64) {
+	st.mutex.RLock()
+	v = st.config.Cache.WebPushSubscriptionIDsMemRatio
+	st.mutex.RUnlock()
+	return
+}
+
+// SetCacheWebPushSubscriptionIDsMemRatio safely sets the Configuration value for state's 'Cache.WebPushSubscriptionIDsMemRatio' field
+func (st *ConfigState) SetCacheWebPushSubscriptionIDsMemRatio(v float64) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.Cache.WebPushSubscriptionIDsMemRatio = v
+	st.reloadToViper()
+}
+
+// CacheWebPushSubscriptionIDsMemRatioFlag returns the flag name for the 'Cache.WebPushSubscriptionIDsMemRatio' field
+func CacheWebPushSubscriptionIDsMemRatioFlag() string {
+	return "cache-web-push-subscription-ids-mem-ratio"
+}
+
+// GetCacheWebPushSubscriptionIDsMemRatio safely fetches the value for global configuration 'Cache.WebPushSubscriptionIDsMemRatio' field
+func GetCacheWebPushSubscriptionIDsMemRatio() float64 {
+	return global.GetCacheWebPushSubscriptionIDsMemRatio()
+}
+
+// SetCacheWebPushSubscriptionIDsMemRatio safely sets the value for global configuration 'Cache.WebPushSubscriptionIDsMemRatio' field
+func SetCacheWebPushSubscriptionIDsMemRatio(v float64) {
+	global.SetCacheWebPushSubscriptionIDsMemRatio(v)
+}
+
 // GetCacheVisibilityMemRatio safely fetches the Configuration value for state's 'Cache.VisibilityMemRatio' field
 func (st *ConfigState) GetCacheVisibilityMemRatio() (v float64) {
 	st.mutex.RLock()