Is your feature request related to a problem? Please describe.
The user will have the ability to import holidays as tasks to the monthly calendar view.

Describe the solution you'd like
Add a new Model class under TodoList/TodoList.Core/Models/:
This will need a new migration for the new UserPreferences table.

class UserPreferences
// In iso-3166 format. 1 for now. _In the fu

In #33 we created an ExpandFrom attribute. We now need to go back and add some documentation and usage examples.

You'll definitely want to read #33 and become familiar with the implementation.

Possible Implementation

1. Adding a tutorial for ExpandFrom to docs
   1a. Add a reference to the Documentation list and the table of contents
2. Add a relevant example usage to the NetCoreExampl