Add support for the Menu Item Extras module

With addition of the menu_item_extras module (the one that adds the possibility to extend simple menu_link_contents with Field UI, and basically transforming it in a fully usable content entity, it also introduces it to the View Modes. The previous patch (although completely functioning and awesome, it lacks the including the info of the view_mode.

I've modified it a little to include the missing info.

I've added event dispatcher to add extra fields for menu response

https://www.drupal.org/project/jsonapi_menu_items/issues/3276561#comment-15099425 works!

Rerolled #7 + added some coding standards fixes

In #13: created a PR from patch #11, and it also adds caching to the getRouteResourceTypes() method, as that was causing memory issues on sites with a large number of menus.

Add language support.

I'll pick this up to review and get merged!

Hiding some patches. Need to see what #15 provides that isn't in the MR. No interdiff, but language support is a good thing. Or it should be done in 🐛 Add langcode & fix content caching Needs work

Wrote a test and it looks like this MR broke when a menu has plugin-based menu links, working on a fix. See https://git.drupalcode.org/project/jsonapi_menu_items/-/merge_requests/1...

The MR addresses #15 by leveraging `\Drupal\menu_link_content\Plugin\Menu\MenuLinkContent::getEntity` which loads the entity from context for the proper translation of entity fields.

Okay, I think this is all set for review now! Thanks everyone for the work. I made it a bit more generic so that if anyone made menu_link_content fieldable without menu_item_extras it also works.

Marking issue credit

This passed several rounds on internal QA on our side, I'm going to merge so we can unblock 🐛 Add langcode & fix content caching Needs work

Automatically closed - issue fixed for 2 weeks with no activity.