web: refactor locale handler into top-level context handler (#6022)

* web: begin refactoring the application for future development

This commit:

- Deletes a bit of code.
- Extracts *all* of the Locale logic into a single folder, turns management of the Locale files over
  to Lit itself, and restricts our responsibility to setting the locale on startup and when the user
  changes the locale. We do this by converting a lot of internal calls into events; a request to
  change a locale isn't a function call, it's an event emitted asking `REQUEST_LOCALE_CHANGE`. We've
  even eliminated the `DETECT_LOCALE_CHANGE` event, which redrew elements with text in them, since
  Lit's own `@localized()` decorator does that for us automagically.
- We wrap our interfaces in an `ak-locale-context` that handles the startup and listens for the
  `REQUEST_LOCALE_CHANGE` event.
- ... and that's pretty much it.  Adding `@localized()` as a default behavior to `AKElement` means
  no more custom localization is needed *anywhere*.

* web: improve the localization experience

This commit fixes the Storybook story for the localization context component,
and fixes the localization initialization pass so that it is only called once
per interface environment initialization.  Since all our interfaces share the
same environment (the Django server), this preserves functionality across
all interfaces.

---------

Co-authored-by: Jens Langhammer <jens@goauthentik.io>

web/src/elements/ak-locale-context/definitions.ts

@@ -0,0 +1,61 @@
+import * as _enLocale from "@goauthentik/locales/en";
+
+import type { LocaleModule } from "@lit/localize";
+import { msg } from "@lit/localize";
+
+import { AkLocale, LocaleRow } from "./types";
+
+export const DEFAULT_FALLBACK = "en";
+
+const enLocale: LocaleModule = _enLocale;
+
+export { enLocale };
+
+// NOTE: This table cannot be made any shorter, despite all the repetition of syntax. Bundlers look
+// for the `await import` string as a *string target* for doing alias substitution, so putting
+// the import in some sort of abstracting function doesn't work. The same is true for the `msg()`
+// function, which `localize` uses to find strings for extraction and translation. Likewise,
+// because this is a file-level table, the `msg()` must be thunked so that they're re-run when
+// the user changes the locale.
+
+// NOTE: The matchers try to conform loosely to [RFC
+// 5646](https://www.rfc-editor.org/rfc/rfc5646.txt), "Tags for the Identification of Languages." In
+// practice, language tags have been seen using both hyphens and underscores, and the Chinese
+// language uses both "regional" and "script" suffixes. The regexes use the language and any region
+// or script.
+//
+// French is currently an oddity; the translator provided the France regional version explicitly,
+// and we fall back to that regardless of region. Sorry, Québécois.
+//
+// Chinese locales usually (but not always) use the script rather than region suffix. The default
+// (optional) fallback for Chinese (zh) is "Chinese (simplified)", which is why it has that odd
+// regex syntax at the end which means "match zh as long as it's not followed by a [:word:] token";
+// Traditional script and the Taiwanese are attempted first, and if neither matches, anything
+// beginning with that generic "zh" is mapped to "Chinese (simplified)."
+
+// - Code for Lit/Locale
+// - Regex for matching user-supplied locale.
+// - Text Label
+// - Locale loader.
+
+// prettier-ignore
+const LOCALE_TABLE: LocaleRow[] = [
+    ["en",      /^en([_-]|$)/i,      () => msg("English"),               async () => await import("@goauthentik/locales/en")],
+    ["es",      /^es([_-]|$)/i,      () => msg("Spanish"),               async () => await import("@goauthentik/locales/es")],
+    ["de",      /^de([_-]|$)/i,      () => msg("German"),                async () => await import("@goauthentik/locales/de")],
+    ["fr_FR",   /^fr([_-]|$)/i,      () => msg("French"),                async () => await import("@goauthentik/locales/fr_FR")],
+    ["pl",      /^pl([_-]|$)/i,      () => msg("Polish"),                async () => await import("@goauthentik/locales/pl")],
+    ["tr",      /^tr([_-]|$)/i,      () => msg("Turkish"),               async () => await import("@goauthentik/locales/tr")],
+    ["zh-Hant", /^zh[_-](HK|Hant)/i, () => msg("Chinese (traditional)"), async () => await import("@goauthentik/locales/zh-Hant")],
+    ["zh_TW",   /^zh[_-]TW$/i,       () => msg("Taiwanese Mandarin"),    async () => await import("@goauthentik/locales/zh_TW")],
+    ["zh-Hans", /^zh(\b|_)/i,        () => msg("Chinese (simplified)"),  async () => await import("@goauthentik/locales/zh-Hans")],
+];
+
+export const LOCALES: AkLocale[] = LOCALE_TABLE.map(([code, match, label, locale]) => ({
+    code,
+    match,
+    label,
+    locale,
+}));
+
+export default LOCALES;