Does the modules applies to group_content_menu link items?

Problem/Motivation

I need to add an image field on link items for a group_content_menu (menu for groups).

Steps to reproduce

Install the module
Edit standard menu, add a field image => OK
Edit Group menu => no option to add a field image.

Is group menu not supported or did I just misconfigure something ?

Proposed resolution

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Remaining tasks

Find a solution to apply menu item extras on group_content_menu.

User interface changes

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API changes

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Data model changes