Codespaces is updating the domain used for forwarded ports

Starting in August, Codespaces will be updating web client port forwarding to improve security, reliability, and performance for users. As part of this update, the URL for forwarded ports will change from https://*.preview.app.github.dev to https://*.app.github.dev.

To prepare for this change, replace any hardcoded references to preview.app.github.dev in your code with the GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN environment variable by July 31 to avoid any disruptions. The environment variable value will be updated from preview.app.github.dev to app.github.dev when the migration completes. Learn more about environments variables here.