[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

vendor/github.com/rivo/uniseg/graphemerules.go

@@ -0,0 +1,176 @@
+package uniseg
+
+// The states of the grapheme cluster parser.
+const (
+	grAny = iota
+	grCR
+	grControlLF
+	grL
+	grLVV
+	grLVTT
+	grPrepend
+	grExtendedPictographic
+	grExtendedPictographicZWJ
+	grRIOdd
+	grRIEven
+)
+
+// The grapheme cluster parser's breaking instructions.
+const (
+	grNoBoundary = iota
+	grBoundary
+)
+
+// grTransitions implements the grapheme cluster parser's state transitions.
+// Maps state and property to a new state, a breaking instruction, and rule
+// number. The breaking instruction always refers to the boundary between the
+// last and next code point. Returns negative values if no transition is found.
+//
+// This function is used as follows:
+//
+//  1. Find specific state + specific property. Stop if found.
+//  2. Find specific state + any property.
+//  3. Find any state + specific property.
+//  4. If only (2) or (3) (but not both) was found, stop.
+//  5. If both (2) and (3) were found, use state from (3) and breaking instruction
+//     from the transition with the lower rule number, prefer (3) if rule numbers
+//     are equal. Stop.
+//  6. Assume grAny and grBoundary.
+//
+// Unicode version 15.0.0.
+func grTransitions(state, prop int) (newState int, newProp int, boundary int) {
+	// It turns out that using a big switch statement is much faster than using
+	// a map.
+
+	switch uint64(state) | uint64(prop)<<32 {
+	// GB5
+	case grAny | prCR<<32:
+		return grCR, grBoundary, 50
+	case grAny | prLF<<32:
+		return grControlLF, grBoundary, 50
+	case grAny | prControl<<32:
+		return grControlLF, grBoundary, 50
+
+	// GB4
+	case grCR | prAny<<32:
+		return grAny, grBoundary, 40
+	case grControlLF | prAny<<32:
+		return grAny, grBoundary, 40
+
+	// GB3
+	case grCR | prLF<<32:
+		return grControlLF, grNoBoundary, 30
+
+	// GB6
+	case grAny | prL<<32:
+		return grL, grBoundary, 9990
+	case grL | prL<<32:
+		return grL, grNoBoundary, 60
+	case grL | prV<<32:
+		return grLVV, grNoBoundary, 60
+	case grL | prLV<<32:
+		return grLVV, grNoBoundary, 60
+	case grL | prLVT<<32:
+		return grLVTT, grNoBoundary, 60
+
+	// GB7
+	case grAny | prLV<<32:
+		return grLVV, grBoundary, 9990
+	case grAny | prV<<32:
+		return grLVV, grBoundary, 9990
+	case grLVV | prV<<32:
+		return grLVV, grNoBoundary, 70
+	case grLVV | prT<<32:
+		return grLVTT, grNoBoundary, 70
+
+	// GB8
+	case grAny | prLVT<<32:
+		return grLVTT, grBoundary, 9990
+	case grAny | prT<<32:
+		return grLVTT, grBoundary, 9990
+	case grLVTT | prT<<32:
+		return grLVTT, grNoBoundary, 80
+
+	// GB9
+	case grAny | prExtend<<32:
+		return grAny, grNoBoundary, 90
+	case grAny | prZWJ<<32:
+		return grAny, grNoBoundary, 90
+
+	// GB9a
+	case grAny | prSpacingMark<<32:
+		return grAny, grNoBoundary, 91
+
+	// GB9b
+	case grAny | prPrepend<<32:
+		return grPrepend, grBoundary, 9990
+	case grPrepend | prAny<<32:
+		return grAny, grNoBoundary, 92
+
+	// GB11
+	case grAny | prExtendedPictographic<<32:
+		return grExtendedPictographic, grBoundary, 9990
+	case grExtendedPictographic | prExtend<<32:
+		return grExtendedPictographic, grNoBoundary, 110
+	case grExtendedPictographic | prZWJ<<32:
+		return grExtendedPictographicZWJ, grNoBoundary, 110
+	case grExtendedPictographicZWJ | prExtendedPictographic<<32:
+		return grExtendedPictographic, grNoBoundary, 110
+
+	// GB12 / GB13
+	case grAny | prRegionalIndicator<<32:
+		return grRIOdd, grBoundary, 9990
+	case grRIOdd | prRegionalIndicator<<32:
+		return grRIEven, grNoBoundary, 120
+	case grRIEven | prRegionalIndicator<<32:
+		return grRIOdd, grBoundary, 120
+	default:
+		return -1, -1, -1
+	}
+}
+
+// transitionGraphemeState determines the new state of the grapheme cluster
+// parser given the current state and the next code point. It also returns the
+// code point's grapheme property (the value mapped by the [graphemeCodePoints]
+// table) and whether a cluster boundary was detected.
+func transitionGraphemeState(state int, r rune) (newState, prop int, boundary bool) {
+	// Determine the property of the next character.
+	prop = propertyGraphemes(r)
+
+	// Find the applicable transition.
+	nextState, nextProp, _ := grTransitions(state, prop)
+	if nextState >= 0 {
+		// We have a specific transition. We'll use it.
+		return nextState, prop, nextProp == grBoundary
+	}
+
+	// No specific transition found. Try the less specific ones.
+	anyPropState, anyPropProp, anyPropRule := grTransitions(state, prAny)
+	anyStateState, anyStateProp, anyStateRule := grTransitions(grAny, prop)
+	if anyPropState >= 0 && anyStateState >= 0 {
+		// Both apply. We'll use a mix (see comments for grTransitions).
+		newState = anyStateState
+		boundary = anyStateProp == grBoundary
+		if anyPropRule < anyStateRule {
+			boundary = anyPropProp == grBoundary
+		}
+		return
+	}
+
+	if anyPropState >= 0 {
+		// We only have a specific state.
+		return anyPropState, prop, anyPropProp == grBoundary
+		// This branch will probably never be reached because okAnyState will
+		// always be true given the current transition map. But we keep it here
+		// for future modifications to the transition map where this may not be
+		// true anymore.
+	}
+
+	if anyStateState >= 0 {
+		// We only have a specific property.
+		return anyStateState, prop, anyStateProp == grBoundary
+	}
+
+	// No known transition. GB999: Any ÷ Any.
+	return grAny, prop, true
+}