make it possible (optional) to restrict access by non company users

In order to comply with the BIR/BIO (government security policy) access to projects should always be based on need to use/need to know. It is quite easy to handle accounts within the own domain, but not with external accounts. 

We would like to see a company-admin new setting to disable the possibility to invite external (non-company) accounts. 

This could be combined with a function to add optional ‘alowed’ external domains (for instance @mendix.com).