I came across a situation in my recent project, where user roles other than admin have to access the admin pages. The default admin theme was not provided for the admin pages in which the user role is not admin. Drupal has a module which allows us to add the admin theme to specific pages irrespective of the user role. Below are the steps which I followed to achieve this.
In one of my recent projects i came across a situation where i had to create a order line item programatically. If you have ever came across such a situation you would end up in line_item_example.module which demonstrate the addition of a new line item type programatically.