[Auto Provision] Extend Provisioning Template (P-Series CE)

The ability to create custom templates is excellent, as an enhancement to that ability it would be greate if you could extend rather than replace the default tempalte.

For example, in the YSDP_YealinkT5 template, I would like to set some extra variables that are not set on the default template.

There is no need for me to replace the template fully however, as if the default template is updated, I will have to copy it over to my new template.

If I was able to extend the template instead, then any updates to the default template would apply to the extended template, leaving my overriden values in place.