[REQUEST]: Add example of Fleet read only user and more

[tailorzed]

Description

We would like to have an updated picture and example here, as we have Fleet with Read privilege in the UI as well. I checked version 8.16.0, but I suspect I have in an earlier version already.

Resources

1. The page https://www.elastic.co/guide/en/fleet/current/fleet-roles-and-privileges.html contains info which is not up to date. The mention Read-only access to Fleet is not currently supported but is planned for development in a later release. seems to be incorrect as we have Read Fleet permissions

2. We should offer the JSON body which describes the permissions required to grant Fleet (all, read) and Integrations (all, read)

Collaboration

Please choose a preferred collaboration model.

Point of contact.

Main contact: @tailorzed

Stakeholders: @lucabelluccini

[lucabelluccini]

FYI @kilfoyle - not urgent but it would be good to track