/ip dns static add address=10.100.10.200 name=haproxy.auriel.local
/ip dhcp-server lease add address=10.100.10.200 comment="HA-proxy container veth" dhcp-option=domain-search mac-address=00:00:00:00:00:01 server=dhcpserver_INTER
/interface/veth add name=veth-haproxy address=10.100.10.200/24 gateway=10.100.10.254
/interface bridge port add bridge=bridge1 interface=veth-haproxy disabled=no hw=no pvid=10
And add as untagged to VLAN 10:
/interface/bridge/vlan edit number=0 untagged
Add veth-haproxy to the list ans save with CRTL-o.