I'm not sure if i want the same as you, so to be clear.
I'm running a shop which sells parts for domestic suppliance. I want my customers to be able to create list of brands & type's machines they own. So when they come to my store, we can see what brand & type vacuum cleaner they own (for example) and sell them the right vacuum bags. I don't want my employers to edit things in the backoffice. They must only be able to see the list with machines. Because of that the information is not "confidential" i want there to be an button on my front page. So when my customer is in my store, they can login with that button by providing there email & password. Any ideas how to do that?