RSPAMD: add more DNSBL like b.barracudacentral.org

Feature
8

Take a look to the comment of @JOduMonT about the number of rbl, some are pre-configured in rspamd, check /etc/rspamd/modules.d/rbl.conf

Anyway this is the generic way to implement a RBL in rspamd, please read also https://rspamd.com/doc/modules/rbl.html

# cat /etc/rspamd/local.d/rbl.conf
rbls {
    brbl {
        symbol = BARRACUDA_RBL;
        rbl = "b.barracudacentral.org";
        received = true;
    }
}

and

# cat /etc/rspamd/local.d/rbl_group.conf
symbols = {

    "BARRACUDA_RBL" {
        weight = 0.0;
        description = "Resolver blocked due to barracuda rbl";
    }
}

adapt the weight to increase the spamd score when the rule matches