Add dynu_dns_record CRUD resource and write-capable client

examples/resources/dynu_dns_record/resource.tf

@@ -0,0 +1,7 @@
+resource "dynu_dns_record" "txt" {
+  hostname    = "api.example.com"
+  record_type = "TXT"
+  content     = "managed-by-terraform"
+  ttl         = 300
+  state       = true
+}