Is your feature request related to a problem? Please describe.
Wireguard doesn't have a blacklist feature for allowedIPs, understandably so because that would add overhead. In order to fine tune allowedIPs, excluding an IPs requires calculating all ranges around them.

Describe the solution you'd like
I want a page to calculate allowedIPs based on allowed and disallowed ips. The web ui already has a nifty Key generator. Extending built-in tooling seems natural.

Describe alternatives you've considered
Alternatives I'm using currently:
https://www.procustodibus.com/blog/2021/03/wireguard-allowedips-calculator/
or
https://github.com/tim-crisp/wireguard-allowed-ips-calculator

Additional context
If excluding IPs from allowedIPs can be built right into the config itself, that would be even better.