Q: Create a new compute engine When creating a new compute engine using the Debian 9.0 image there is a default user created with my full email address. This user has no primary group associated with it.
How do I setup this user so that it has a valid primary group on creation?
If I type 'id' on my user I get the following; 
uid=53928310(foo_gmail_com) gid=53928310 groups=53928310

The GID 53928310 doesn't exist in the /etc/group file I have to 
sudo addgroup --gid 53928310 foo_gmail_com

Also the user doesn't exist in the /etc/passwd file, should it?

A: I can see the user ID and group ID is showing the output of ID command, as such the user and group ID should exist in the /etc/passwd.
The issue seems to be a transient error with user creation. In order to work around this issue, you can ssh from the browser and change the user. By so doing it will generate another user and add it to right group i.e same as username.
Steps to change the user from ssh from the browser are documented here.
