Use two-step fact assignment for Vultr startup script

Changed to set the cloud-init script as a fact first, then reference
that fact in the startup_script module. This follows the pattern used
by the Linode provider and avoids JSON serialization issues with nested
template lookups.

This approach ensures the template is fully evaluated and stored as a
string before being passed to the vultr.cloud.startup_script module,
which then base64-encodes it for the API.

Related to: JSON serialization with "tagless" profile in Ansible 2.19+

Author: fank

roles/cloud-vultr/tasks/main.yml

@@ -3,6 +3,10 @@
   import_tasks: prompts.yml
 
 - block:
+    - name: Set cloud-init script as fact
+      set_fact:
+        algo_cloud_init_script: "{{ lookup('template', 'files/cloud-init/base.yml') }}"
+
     - name: Creating a firewall group
       vultr.cloud.firewall_group:
         name: "{{ algo_server_name }}"
@@ -28,7 +32,7 @@
     - name: Upload the startup script
       vultr.cloud.startup_script:
         name: algo-startup
-        script: "{{ lookup('template', 'files/cloud-init/base.yml') | string }}"
+        script: "{{ algo_cloud_init_script }}"
 
     - name: Creating a server
       vultr.cloud.instance: