[feature request] support DNAT on the NAT output chain

I want to redirect all traffic from LAN to WAN IP1 (or an ipset) to WAN IP2. For now, this can be accomplished by the DNAT rule:

config redirect
        option target 'DNAT'
        option name 'IP1-IP2'
        option family 'ipv4'
        option src 'lan'
        option ipset 'IPSET1'
        option dest_ip 'IP2'
        list proto 'all'

which will generate the following nftables rule:

chain dstnat_lan {
        ip daddr @IPSET1 counter packets 0 bytes 0 dnat ip to IP2 comment "!fw4: IP1-IP2"
}

However, the dstnat_lan chain is part of the nat postrouting chain so it will apply to devices behind the router, not the router itself.

To enable the redirection for the router, I have to resort to a custom nftables rule:

chain user_pre_output_nat {
    type nat hook output priority -1; policy accept;
    ip daddr @IPSET1 counter dnat ip to IP2
}

Please make fw4 capable of generating DNAT rules on the nat output chain that suppresses my custom rule.

Start by tracing how fw4 generates the dstnat_lan chain and how the user_pre_output_nat chain is attached. Confirm the desired behavior with LAN-to-WAN traffic targeting IP1 or IPSET1, then verify that generated nftables output-chain rules redirect router-originated traffic to IP2 without requiring a custom rule.