Usermeta not stored for super-admin

[sebastienserre]

On a multisite context, a super-admin has access to all websites of the multisite but the user is not added as a user of the website.

As a result, in a block editor context, if we update a user_meta for a super admin, the route ​http://localhost:8888/sub-site/wp-json/wp/v2/users/me is returning a 404 error.

In Polylang Pro, we're updating a usermeta according to settings on a post edit page. This setting is not stored in the super-admin usermeta.

The workaround we have found is to manually add the super-admin as an existing user on the subsite to make the route available.

We think, a super-admin should be automatically added as Administrator on each website of the network.