Captive portal and user registration

[Leviathan]

Good evening guys.
I ask for your help with an issue on which I am having some difficulties not knowing OPNsense in depth and coming from other platforms: I would need to enable the captive portal for the vlan dedicated to wifi.
We were evaluating with colleagues to enable it both with the local database (those who already have, for example the vpn credentials, could connect with those credentials) and with the vouchers.
Enabled in this way it works correctly and without problems ... the problem with vouchers is that sending username and pass individually to each of the users (being several hundred users) is not exactly convenient, not to mention that in case of loss of credentials we could have a problem.
Is there a way to create a local database or a login server where the password could be, for example, the company email that every employee has? By entering, perhaps, these values ​​en masse through a csv file or similar and using these credentials to allow staff to log in?
Or a way of allowing staff to register exclusively with the email address n.surname@company.it, automatically discarding any other email not belonging to the company domain?
Thanks in advance for the answers and for the support.