Hello,
There is another thread on this topic if you don't want to use RADIUS
PPSK with RADIUS on OpenWrt also works well.
I am in the process of completing the integration with RADIUSdesk and MESHdesk/APdesk although it is not fully complete yet.
When it is complete it will include redirecting unknown users to a captive portal to register and choose their PSK and also the ability to do daily, weekly and monthly data limits.
(This will all be fully Open Source)