[chore] Validate/set account domain (#619)

* add miekg/dns dependency

* set/validate accountDomain

vendor/golang.org/x/net/ipv6/zsys_openbsd.go

@@ -0,0 +1,42 @@
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
+// cgo -godefs defs_openbsd.go
+
+package ipv6
+
+const (
+	sizeofSockaddrInet6 = 0x1c
+	sizeofInet6Pktinfo  = 0x14
+	sizeofIPv6Mtuinfo   = 0x20
+
+	sizeofIPv6Mreq = 0x14
+
+	sizeofICMPv6Filter = 0x20
+)
+
+type sockaddrInet6 struct {
+	Len      uint8
+	Family   uint8
+	Port     uint16
+	Flowinfo uint32
+	Addr     [16]byte /* in6_addr */
+	Scope_id uint32
+}
+
+type inet6Pktinfo struct {
+	Addr    [16]byte /* in6_addr */
+	Ifindex uint32
+}
+
+type ipv6Mtuinfo struct {
+	Addr sockaddrInet6
+	Mtu  uint32
+}
+
+type ipv6Mreq struct {
+	Multiaddr [16]byte /* in6_addr */
+	Interface uint32
+}
+
+type icmpv6Filter struct {
+	Filt [8]uint32
+}