add AXFR request handling to support slaves

pkg/acmedns/interfaces.go

@@ -10,6 +10,7 @@ type AcmednsDB interface {
 	Register(cidrslice Cidrslice) (ACMETxt, error)
 	GetByUsername(uuid.UUID) (ACMETxt, error)
 	GetTXTForDomain(string) ([]string, error)
+	GetTXTForAllDomains() ([]TXTRecord, error)
 	Update(ACMETxtPost) error
 	GetBackend() *sql.DB
 	SetBackend(*sql.DB)
@@ -23,4 +24,8 @@ type AcmednsNS interface {
 	ParseRecords()
 	BumpSerial() error
 }
+
+type TXTRecord struct {
+	Subdomain string
+	Value     string
 }