Is it possible to get the link to the message using Google API? Can message id be translated somehow to direct link which can be opened in browser?
You can try with URL https://mail.google.com/mail/#inbox/messageId. But you should have access to this message. But this URL is generated by Gmail UI not with API. So, you have to create the above URL in your program
https://mail.google.com/mail/#inbox/messageId