Can I get a link to a message using the Google API? Can a message identifier somehow translate a link that can be opened in a browser?
You can try with the URL https://mail.google.com/mail/#inbox/messageId . But you must have access to this post. But this URL is generated by the Gmail user interface, not the API. So you must create the above url in your program
https://mail.google.com/mail/#inbox/messageId