certbot(role): support DNS-01 certs using acme-dns

Introduce new configuration structure called certbot__certs, which
allows for different challenge types per cert with the first challenge
type supported being dns-01-acme-dns.

roles/certbot/tasks/main/validate_cert.yaml

@@ -0,0 +1,31 @@
+- name: validate dns-01-acme-dns challenge type config
+  when: item.challengeType == "dns-01-acme-dns"
+  block:
+    - name: assert dns_01_acme_dns config exists
+      ansible.builtin.assert:
+        that: item.dns_01_acme_dns is defined
+
+    - name: assert dns_01_acme_dns config is valid
+      ansible.builtin.validate_argument_spec:
+        argument_spec: "{{ required_data }}"
+        provided_arguments:
+          dns_01_acme_dns: "{{ item.dns_01_acme_dns }}"
+      vars:
+        required_data:
+          dns_01_acme_dns:
+            type: dict
+            required: true
+            options:
+              serverUrl:
+                type: str
+                required: false
+                default: https://acmedns.hamburg.ccc.de
+              subdomain:
+                type: str
+                required: true
+              apiUser:
+                type: str
+                required: true
+              apiKey:
+                type: str
+                required: true