Convert certbot role to use standalone instead of webroot

Do this to not have dependencies on an NGINX setup.
With those dependencies in place setting up the certificates initially
would be quite painful, since a half-configured NGINX would need to be
there for the challenge and then only after the certificates are
present, the full NGINX configuration could be deployed successfully.

playbooks/roles/certbot/tasks/main/cert.yaml

@@ -6,7 +6,7 @@
   register: certbot__cert_expiry_before
 
 - name: obtain the certificate using certbot
-  ansible.builtin.command: /usr/bin/certbot certonly --keep-until-expiring --agree-tos --non-interactive --email "{{ certbot__acme_account_email_address }}" --no-eff-email --webroot --webroot-path /webroot-for-acme-challenge -d "{{ item }}"
+  ansible.builtin.command: /usr/bin/certbot certonly --keep-until-expiring --agree-tos --non-interactive --email "{{ certbot__acme_account_email_address }}" --no-eff-email --standalone --http-01-port 31820 -d "{{ item }}"
   become: true
   changed_when: false
 

playbooks/roles/certbot/tasks/main/certs.yaml

@@ -1,12 +1,3 @@
-- name: ensure directory for the webroot exists
-  ansible.builtin.file:
-    path: /webroot-for-acme-challenge/
-    state: directory
-    mode: "0755"
-    owner: root
-    group: root
-  become: true
-
 - name: obtain certificates
   loop: "{{ certbot__certificate_domains }}"
   ansible.builtin.include_tasks: