Using flow to create and update tasks in Planner

Hi,

I have created a flow that watches a SharePoint folder and creates a ask in planner - works fine. However I want to either create a URL to the file, or add the file as a attachment, and I cannot see how! I have tried many of the solutions posted on the forum (like this one <a href=URL>@{triggerOutputs()?['headers/x-ms-file-id']}​</a>) however nothing seems to work.