FirebaseAdmin. Messaging. WebpushFcmOptions
  Represents the Webpush-specific notification options that can be included in a Message.
Summary
See REST API reference for a list of supported fields.
        Properties | 
    |
|---|---|
        Link
       | 
      
        string
        Gets or sets the link to open when the user clicks on the notification.  
       | 
    
Properties
Link
string Link
Gets or sets the link to open when the user clicks on the notification.
For all URL values, HTTPS is required.