[NextJs] i18n updates

[ambrauer]

Updates after further i18n analysis / testing, including:

• Consolidate default language/locale settings (always defer to package.json config language)
• Allow sample to run with Next.js i18n disabled
• Add locale variations of configured rewrites (for Sitecore requests pass-through e.g. /sitecore, /media, /layouts)
• Upgraded next-localization (w/ rosetta) library as dictionary solution of choice. Simplified usage examples. Updated comments in _app.tsx.
• Remove export scripts for now (since it doesn't work with next.js v10 i18n and image optimization), to be addressed in separate task

Known limitations / open issues:

• Root page client-side route for 'da-DK' shows 404
  • Repro: go to http://localhost:3000/da-DK/styleguide, click on logo > get 404
  • Direct request for http://localhost:3000/da-DK works fine (refresh page)
  • RESOLUTION: Known issue with fix in Next.js, confirmed fixed with latest canary build
• i18n support is not compatible with next export
• Cannot force sub-path/prefix usage for default locale
  • Currently breaking test for multilingual styleguide component (English href is "/styleguide" instead of expected "/en/styleguide")
  • Would be preferred with "always" languageEmbedding in Sitecore
  • This doesn't mean it won't resolve the route, just that next/link does not add it
  • RESOLUTION:
    • Fix/enhancement is in the works in Next.js
    • In the meantime, workaround would be to add the prefix yourself in all client routing. e.g.

    <Link href={`${router.locale}/styleguide`} locale={false}>
      <a className="p-2 text-dark">{i18n.t('Styleguide')}</a>
    </Link>
    

[sc-illiakovalenko]

@ambrauer For me, everything is fine. Will we store somewhere these limitations/issues?

[ambrauer]

@sc-illiakovalenko Yep, these limitations are covered in docs and/or backlog items.