Extend testing of the autocreate plugin

[nrobinaubertin]

Enhancement Proposal

The following PR #220 introduced an indico plugin that enhances indico's CLI by adding an automated way to create admin users.
The actual tests make sure that the charm action calls the plugin via indico's CLI but not that the plugin itself is correct.
This lead to a long discussion on the subject that ultimately resulted in this issue.

[alithethird]

@nrobinaubertin what is the status here?

[nrobinaubertin]

It never was added to our roadmap. But it is not necessary in my opinion