[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/doc.go

@@ -0,0 +1,108 @@
+/*
+Package uniseg implements Unicode Text Segmentation, Unicode Line Breaking, and
+string width calculation for monospace fonts. Unicode Text Segmentation conforms
+to Unicode Standard Annex #29 (https://unicode.org/reports/tr29/) and Unicode
+Line Breaking conforms to Unicode Standard Annex #14
+(https://unicode.org/reports/tr14/).
+
+In short, using this package, you can split a string into grapheme clusters
+(what people would usually refer to as a "character"), into words, and into
+sentences. Or, in its simplest case, this package allows you to count the number
+of characters in a string, especially when it contains complex characters such
+as emojis, combining characters, or characters from Asian, Arabic, Hebrew, or
+other languages. Additionally, you can use it to implement line breaking (or
+"word wrapping"), that is, to determine where text can be broken over to the
+next line when the width of the line is not big enough to fit the entire text.
+Finally, you can use it to calculate the display width of a string for monospace
+fonts.
+
+# Getting Started
+
+If you just want to count the number of characters in a string, you can use
+[GraphemeClusterCount]. If you want to determine the display width of a string,
+you can use [StringWidth]. If you want to iterate over a string, you can use
+[Step], [StepString], or the [Graphemes] class (more convenient but less
+performant). This will provide you with all information: grapheme clusters,
+word boundaries, sentence boundaries, line breaks, and monospace character
+widths. The specialized functions [FirstGraphemeCluster],
+[FirstGraphemeClusterInString], [FirstWord], [FirstWordInString],
+[FirstSentence], and [FirstSentenceInString] can be used if only one type of
+information is needed.
+
+# Grapheme Clusters
+
+Consider the rainbow flag emoji: 🏳️‍🌈. On most modern systems, it appears as one
+character. But its string representation actually has 14 bytes, so counting
+bytes (or using len("🏳️‍🌈")) will not work as expected. Counting runes won't,
+either: The flag has 4 Unicode code points, thus 4 runes. The stdlib function
+utf8.RuneCountInString("🏳️‍🌈") and len([]rune("🏳️‍🌈")) will both return 4.
+
+The [GraphemeClusterCount] function will return 1 for the rainbow flag emoji.
+The Graphemes class and a variety of functions in this package will allow you to
+split strings into its grapheme clusters.
+
+# Word Boundaries
+
+Word boundaries are used in a number of different contexts. The most familiar
+ones are selection (double-click mouse selection), cursor movement ("move to
+next word" control-arrow keys), and the dialog option "Whole Word Search" for
+search and replace. This package provides methods for determining word
+boundaries.
+
+# Sentence Boundaries
+
+Sentence boundaries are often used for triple-click or some other method of
+selecting or iterating through blocks of text that are larger than single words.
+They are also used to determine whether words occur within the same sentence in
+database queries. This package provides methods for determining sentence
+boundaries.
+
+# Line Breaking
+
+Line breaking, also known as word wrapping, is the process of breaking a section
+of text into lines such that it will fit in the available width of a page,
+window or other display area. This package provides methods to determine the
+positions in a string where a line must be broken, may be broken, or must not be
+broken.
+
+# Monospace Width
+
+Monospace width, as referred to in this package, is the width of a string in a
+monospace font. This is commonly used in terminal user interfaces or text
+displays or editors that don't support proportional fonts. A width of 1
+corresponds to a single character cell. The C function [wcswidth()] and its
+implementation in other programming languages is in widespread use for the same
+purpose. However, there is no standard for the calculation of such widths, and
+this package differs from wcswidth() in a number of ways, presumably to generate
+more visually pleasing results.
+
+To start, we assume that every code point has a width of 1, with the following
+exceptions:
+
+  - Code points with grapheme cluster break properties Control, CR, LF, Extend,
+    and ZWJ have a width of 0.
+  - U+2E3A, Two-Em Dash, has a width of 3.
+  - U+2E3B, Three-Em Dash, has a width of 4.
+  - Characters with the East-Asian Width properties "Fullwidth" (F) and "Wide"
+    (W) have a width of 2. (Properties "Ambiguous" (A) and "Neutral" (N) both
+    have a width of 1.)
+  - Code points with grapheme cluster break property Regional Indicator have a
+    width of 2.
+  - Code points with grapheme cluster break property Extended Pictographic have
+    a width of 2, unless their Emoji Presentation flag is "No", in which case
+    the width is 1.
+
+For Hangul grapheme clusters composed of conjoining Jamo and for Regional
+Indicators (flags), all code points except the first one have a width of 0. For
+grapheme clusters starting with an Extended Pictographic, any additional code
+point will force a total width of 2, except if the Variation Selector-15
+(U+FE0E) is included, in which case the total width is always 1. Grapheme
+clusters ending with Variation Selector-16 (U+FE0F) have a width of 2.
+
+Note that whether these widths appear correct depends on your application's
+render engine, to which extent it conforms to the Unicode Standard, and its
+choice of font.
+
+[wcswidth()]: https://man7.org/linux/man-pages/man3/wcswidth.3.html
+*/
+package uniseg