Get the possibility to have a sub-list

Hi everyone 👋

As a web developer, I would like to add a sub-list to a NcAppNavigationItem component.

In fact, I would like to get an equivalent of this HTML code :

<ul>
  <li>Countries</li>
  <ul>
    <li>France</li>
    <ul>
      <li>Paris</li>
      <li>Roubaix</li>
    </ul>
    <li>Geremany</li>
    <ul>
      <li>Berlin</li>
      <li>Munich</li>
    </ul>
  </ul>
</ul>

Currently, it's not possible. Because, the NcAppNavigation component gives developers just one level of a <ul> html element.

We can write an equivalent to this code :

<NcAppNavigation>
 <template #list>
   <NcAppNavigationItem name="Countries" />
   <ul>
      <NcAppNavigationItem name="Paris" />
      <NcAppNavigationItem name="Roubaix" />
   </ul>
 </template>
</NcAppNavigation>

However, this requires to apply a custom css and it may break Nextcloud's flow design.

What do you think ?

Start by reading src/components/NcAppNavigation/NcAppNavigation.vue at the referenced lines and the linked NcAppNavigationItem documentation. Clarify the supported nested-list behavior and how it should preserve Nextcloud’s flow design; the issue names no test file, so completion should include a verified nested-navigation result.