Ensure cron install

tasks/renew-cron.yml

@@ -1,4 +1,9 @@
 ---
+- name: Install cron package (if not present).
+  package:
+    name: "{{ certbot_cron_package }}"
+    state: present
+
 - name: Add cron job for certbot renewal (if configured).
   cron:
     name: Certbot automatic renewal.

vars/default.yml

@@ -1,3 +1,4 @@
 ---
 certbot_package: certbot
 certbot_dns_cloudflare_package: python3-certbot-dns-cloudflare
+certbot_cron_package: cron