Delete the registry using the following
curl --location \
--request DELETE 'https://api.ionos.com/containerregistries/registries/789f8e3c-d5c8-4359-8f85-c200fb89e97c' \
--header 'Authorization: Basic e3t1c2VybmFtZX19Ont7cGFzc3dvcmR9fQ==' \
204 - No Content
The request was successfully fulfilled and there is no content in the body.
404 Bad Request - Not Found
"msg": "Not Found"
This way you can delete the registry completely.