Language selection and suggestion UX improvements (#9067)

* feat: don't retain accepted language suggestion after finishing or exiting post (#8886)

* feat: don't retain accepted language suggestion after finishing or exiting post

* fix: rebase fixes

* fix: rebase fixes

* chore: lint

* Rename onChange for clarity

* Improve logic in composer

* Handle user override more explicitly

* Drill in onSelectLanguage callback into dialog too

* Fix typo

Co-authored-by: surfdude29 <149612116+surfdude29@users.noreply.github.com>

* Make text crystal clear

* Handle multiple languages

---------

Co-authored-by: Elijah Seed-Arita <elijaharita@gmail.com>
Co-authored-by: surfdude29 <149612116+surfdude29@users.noreply.github.com>

src/state/persisted/schema.ts

@@ -71,7 +71,7 @@ const schema = z.object({
     contentLanguages: z.array(z.string()),
     /**
      * The language(s) the user is currently posting in, configured within the
-     * composer. Multiple languages are psearate by commas.
+     * composer. Multiple languages are separated by commas.
      *
      * BCP-47 2-letter language code without region.
      */

src/state/preferences/languages.tsx

@@ -156,6 +156,10 @@ export function toPostLanguages(postLanguage: string): string[] {
   return postLanguage.split(',').filter(Boolean)
 }
 
+export function fromPostLanguages(languages: string[]): string {
+  return languages.filter(Boolean).join(',')
+}
+
 export function hasPostLanguage(postLanguage: string, code2: string): boolean {
   return toPostLanguages(postLanguage).includes(code2)
 }