The Visual SPA Editor started out using a `templateScript` property in a page template definition.

The "External SPA" feature which introduced `baseUrl` and `routeTemplate` and is now the best practice approach.

In order to get our customers on the better featured External SPA, and to reduce maintenance effort and bugs we should docu deprecate the earlier approach.

To docu:

Short overview of migrating from templateScript approach.

Brief explanation of benefits.

Support will be removed in 6.3.
Will not be supported on SaaS

(Deprecated in 6.2.30)