Handling a TFS 2018 Upgrade from Old Form to New Form

This post announces the deprecation of the old work item form's `<Layout>` tag in TFS 2017.2 and its removal in TFS 2018. It outlines the mandatory upgrade process which will transform work item type definitions to use the `<WebLayout>` element and remove legacy custom controls. It provides a three-step process for users to refine their templates in a pre-production environment, export them, and upload them post-upgrade. For legacy custom controls built by Microsoft, it directs users to the VSTS Marketplace for new controls and advises converting other custom controls to the new REST-based extensibility model using the Work Item Form Service.