Update the wizard 3rd step so that it is optional

Description

With the new organization endpoint update, we'd be able to understand how many users belong to the current organization, using the members field.

On step 3 we need to check if the members list is greater than 1. If so, we'd then let the user close the window without invited users, by clicking a button that must be displayed on the right of the Invitation button. If there isn't more than 1 member the user will not be able to close the window.

Depends on backend#166 (closed)