I did some digging by setting up two differenet Laravel instances. The first worked out of the box. The second worked up until the point were I modified the Cats.php model.
The modified Cats.php model had the following primary key variable set:
protected $primaryKey = 'kittykat_id';
Subsequent logins after the change resulted in the login process redirecting me back to the login page. Both instances worked as designed when there was no modifications to the primaryKey.
When I removed this protected primary key variable I was able to log in to the users table as well as any other table I created to store cats (aka users) and their passwords.
Adding the following protected key to my Cats.php class confirmed the above.
protected $primaryKey = 'id';
So by default the Authenticatable.php class is using avendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php Class to retrieve the primaryKey
Is there any way to use a different primaryKey database column for authentication AND still use Eloquent?