container: add switch for hcloud

roles/prometheus/meta/argument_specs.yml

@@ -19,10 +19,15 @@ argument_specs:
         type: str
         required: false
         default: 3650d
-      prometheus_hcloud_token:
-        description: Access token for hetzner cloud service discovery. It will be enabled if this variable is defined
-        type: str
+      prometheus_hcloud_enabled:
+        description: Whether to use hcloud discovery
+        type: bool
         required: false
+        default: false
+      prometheus_hcloud_token:
+        description: Access token for hetzner cloud service discovery.
+        type: str
+        required: "{{ prometheus_hcloud_enabled }}"
       prometheus_hcloud_relabel_configs:
         description: Relabel configs for hcloud
         type: list