Requesting support to create menu entries with properties using a content adapter, per feedback in my forum post.

In #12507, @jmooring requested support for menu entry creation in content adapters. The resulting implementation in 245928a supports defining flat menu entries:

However, it's not possible to create menu entries with properties within a content adapter, equivalent to defining the following in front matter:

menus:
  main:
    parent: main-page
    identifier: example-id

I expected that passing a map would work:

{{- $mainMenu := dict 
    "parent" "main-page"
    "identifier" "example-id"
-}}
{{- $menus := dict "main" $mainMenu -}}
{{- .AddPage (dict "menus" $menus [...]) -}}

But it seems menus are defined as an array of strings. Maybe it should be a map, like Params?

Thank you!