Docs
The notification
A push carries a title, a body, an image, and a link.
What arrives
The image is attached on the device. If the image fails, the text still arrives. The expanded view shows the large image, the title, the body, and a button.
Where the link opens
The link can be a screen inside the app or an https address. The app opens the screen when it knows the address. An unknown https address opens in the system browser.