Generative Answers provide responses over public websites and content stored in SharePoint and OneDrive. How can I dynamically set the URL value for Generative Answers?

Generative Answers provide responses over public websites and content stored in SharePoint and OneDrive. How can I dynamically set the URL value for Generative Answers?
The "Create generative answers" node expects a table of URLs. Here is how to create a table containing a single URL and pass that value to Generative Answers.
kind: AdaptiveDialog
beginDialog:
kind: OnUnknownIntent
id: main
priority: -1
actions:
- kind: Question
id: question_4mxROI
interruptionPolicy:
allowInterruption: true
variable: init:Topic.url
prompt: Please provide a URL for a public website
entity: StringPrebuiltEntity
- kind: SearchAndSummarizeContent
id: searchAndSummarizeContent_8xHKG5
userInput: =System.Activity.Text
publicDataSource:
sites: =[Topic.url]
sharePointSearchDataSource: {}
customDataSource: {}
The result: