Design a schema and create the necessary migrations and models to represent citizens living in a nation:

Citizen

• Citizens must have a first name and a last name.
• Citizens can optionally have a phone number.
• Citizens can belong to multiple nations.

Nation

• A nation must have a name.
• A nation can optionally have an official language.
• A nation can have many citizens.

Tips

• You should feel free to add whatever additional migrations/models etc. you need to make these associations work.
• This challenge is focused solely on migrations, models, and the database schema. The relevant files that will be checked are:
  • All files in the app/models directory.
  • All files in the db/migrate directory.
  • The db/schema.rb file.
• Include database constraints and model validations where appropriate.
• Draw out the ER Diagram on paper so that you can understand what data you will need to save and the relationships that you will need to create.
• Test your models in pry by running pry -r "./app.rb".
• You do not need to add any routes to the application to make the app functional.