Define a certificates resolver

roles/traefik/templates/traefik.yml.j2

@@ -20,3 +20,16 @@ entrypoints:
     address: ':443'
     http:
       tls: {}
+
+{% if traefik_acme_email is defined %}
+certificatesResolvers:
+  resolver:
+    acme:
+      email: {{ traefik_acme_email }}
+      storage: /etc/traefik/acme.json
+      {% if not traefik_production -%}
+      caServer: https://acme-staging-v02.api.letsencrypt.org/directory
+      {% endif -%}
+      httpChallenge:
+        entryPoint: web
+{% endif %}