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

* add miekg/dns dependency

* set/validate accountDomain

vendor/golang.org/x/net/ipv4/zsys_openbsd.go

@@ -0,0 +1,13 @@
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
+// cgo -godefs defs_openbsd.go
+
+package ipv4
+
+const (
+	sizeofIPMreq = 0x8
+)
+
+type ipMreq struct {
+	Multiaddr [4]byte /* in_addr */
+	Interface [4]byte /* in_addr */
+}