feat: mvp (#1)

MVP including features:
* Detect IP change
* Configurable/generic external IP provider
* Configurable/generic DNS provider
* Impl. of plain external IP provider
* Impl. of Ionos DNS provider

Reviewed-on: #1
Co-authored-by: Timo Behrendt <t.behrendt@t00n.de>
Co-committed-by: Timo Behrendt <t.behrendt@t00n.de>

model/common/common.go

@@ -0,0 +1,9 @@
+package common
+
+type ARecord struct {
+	Domain   string
+	IP       string
+	TTL      int
+	Prio     int
+	Disabled bool
+}