add IONOS Cloud DNS API guidelines

dnsapi2.md

@@ -90,6 +90,7 @@
 - [166. Use myLoc.de / webtropia.com DNS API](#dns_myloc)
 - [167. Use Yandex 360 for Business DNS API](#dns_yandex360)
 - [168. Use HE DNS DDNS API](#dns_he_ddns)
+- [169. Using the IONOS Cloud DNS API](#dns_ionos_cloud)
 - [Use custom API](#dns_myapi)
 - [Use lexicon DNS API](#dns_lexicon)
 
@@ -2266,7 +2267,6 @@ When using OAuth you will need to complete a one-time authorization procedure:
 - [You can learn more about obtaining debug tokens here.](https://yandex.ru/dev/id/doc/ru/tokens/debug-token)
 - [Report any bugs or issues here.](https://github.com/acmesh-official/acme.sh/issues/5213)
 
-
 <a name="dns_he_ddns"/>
 
 ## 168. Use HE DDNS DNS API
@@ -2291,6 +2291,28 @@ The `HE_DDNS_KEY` will be saved in `~/.acme.sh/account.conf` and will be reused
 
 Report any bugs or issues [here](https://github.com/acmesh-official/acme.sh/issues/5238)
 
+<a name="dns_ionos_cloud"/>
+
+## 169. Using the IONOS Cloud DNS API
+
+For informations on how to obtain a token, please read the IONOS cloud api [documentation](https://docs.ionos.com/reference/readme/get-started#authorization).
+
+Please note that [IONOS Cloud DNS](https://docs.ionos.com/cloud/network-services/cloud-dns) API is different from [IONOS core API](https://github.com/acmesh-official/acme.sh/wiki/dnsapi2#129-using-the-ionos-domain-api)
+
+After obtaining token, you need to export it as an environment variable:
+
+```
+export IONOS_TOKEN="..."
+```
+
+Then, you can issue a certificate, by executing:
+
+```
+./acme.sh --issue --dns dns_ionos_cloud -d example.com
+```
+
+Please Report any bugs or issues [here](https://github.com/acmesh-official/acme.sh/issues/5243)
+
 
 <a name="dns_myapi"/>