Switch locale to zh_CN for JH users who not logged in

Issue link

#90

Proposal

We can not directly change the default language of Rails App to zh_CN, which will cause some known and unknown effects.

Reference comment:

• #90 (comment 439766)
• https://gitlab.com/gitlab-jh/gitlab/-/issues/327#note_737839931

Logged-in users can set their own preferred language to change the language display on the page.

Currently, unlogged-in users are shown pages in English, especially the login and register pages.

We need to change the default language of these pages to Chinese.

Code

Apply switch_locale for those Controller througn around_action.

Referance Rails Doc: https://guides.rubyonrails.org/i18n.html#managing-the-locale-across-requests