Feature: Updated spam protection or captcha integration

[arnelap]

As WpBruiser seems to be abandoned, while it is still working perfectly fine right now and it's code seems to be stable, at some point an alternative spam protection would be required.

Maybe we can implement some of the techniques that WpBruiser uses into our plugin (mostly finger-printing) or we can re-create a captcha integration with eg. Google reCaptcha v3 or another provider.