This allows you to for example specify a specific certificate/key on an
serversonly port and in link block (a self-signed 10 year valid certificate)
and use a short-lived (XX day) Let's Encrypt certificate on the other ports.
And several other uses, of course.
Accepted values are: All (enable all), TLSv1, TLSv1.1, TLSv1.2
You can use + and - modifiers, in fact you are encouraged to.
Example: set { ssl { protocols "All,-TLSv1,-TLSv1.1"; }; };
This will only allow TLSv1.2 at time of writing, and later whenever
TLSv1.3 is released it will allow TLSv1.2 and TLSv1.3.
Note that 'SSLv2' and 'SSLv3' do not exist, as UnrealIRCd 4.x never
supported these old versions (and never will).
Bram Matthys