Main menu target in another languages

[jean-gui]

Some entries in the main menu link to pages that are not translated (Groups->Working Groups, Groups->Interest Groups for example).
We will want those menu entries in the Chinese and Japanese versions but we need to specify that the target is in English.
For that I propose that we:

• add a field to menu entries to choose the language of the target link
• use this info in the frontend to add an hreflang
• add a visual clue that the target is in another language. This needs to be accessible as well (but perhaps hreflang is enough for that)

[vivienlacourba]

We plan to launch the new Chinese website in September 2025 so it should be addressed before.

[JamieC24]

We could alternatively add a "language" item to the GraphQL query, which would return the language of the target page. This could then be used as the basis for the hfreflang and visual cue without the need to add an additional field in the CMS. If you're happy with this I can look at implementing that.

[JamieC24]

I've added a new branch called hotfix/#517-menu-target-lang to the craft, frontend and template bundles repos.

This adds a "targetLinkLanguage" field that can be set to (currently): English, Chinese or Japanese.

I have added a check on the navigation template bundle item to check the current site language against the set targetLinkLanguage field, and if they're different, a hreflang is added to the relevant anchor link with a value of the language code of the chosen language (e.g en).

I'm currently consulting the design team on the best visual approach to the visual cue for the language difference. Once I've been advised on this, I'll update this ticket.