Try: Register plugins under separate navigation menu

[joshuatf]

Update the nav to the "Plugins" approach.

Fixes #5530

• Locks core menu items, creating dependency on WCA features within the navigation.
• Adds methods to register plugin categories and items.
• Adds extensions group to client.
• Updates the example plugin.

Note: this PR does not update the styling to the group title "Extensions." The group title styling is different than that shown in #5530. I think this is something we may want to tackle upstream.

Screenshots

Detailed test instructions:

1. Run the extension npm run example -- --ext=add-navigation-items and activate.
2. Note the extensions group and items/categories.
3. Make sure you can't register items in the main menu.
4. Make sure all relevant nav items still exist in the core nav menu.

[octaedro]

Thank you @joshuatf for the great work! This is testing well here and code LGTM

[elizaan36]

hey @joshuatf I think the styling for the extensions header is fine here, and as you mentioned we can consider updating that in the near future.

Wanted to confirm, when there are no extensions installed the extensions section won't appear in the nav?

[joshuatf]

Wanted to confirm, when there are no extensions installed the extensions section won't appear in the nav?

That's correct, @elizaan36 - the Extensions section will be hidden if no plugins have registered there 🙂

[psealock]

@joshuatf, this is a nice addition with nav_args. Small change, but I'm thinking id could also go under nav_args since its used only for matching a slot with the client's fill.