Invitations / applications: global roles, orgs,

Description

Polishing the functionality around invitations / applications

Making the invitation / application process as smooth as possible

Invitations / applications are the first steps users often have with Alkemio, so it has to be a smooth experience

[ ] Expand Community invite functionality with the option to invite for lead or admin role
[ ] Remove admins able to add members at subspace level
[ ] Allow invitations to organizations: generic in that it supports any contributor to be associated, but for now only Users are allowed

S&D