change default value

[benoitblais-hashicorp]

Overview/Summary

Change default value for add_on_description and template_description.

This PR fixes/adds/changes/removes

• Change default value for add_on_description and template_description.

Checklist before requesting a review

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings