Description:
    Creates a new foreign key migration based on your current associations.
    Pass the migration name, either CamelCased or under_scored.

    A migration class is generated in db/migrate prefixed by a timestamp of the
    current date and time. It will contain add_foreign_key calls to create any
    foreign keys that do not already exist (inferred from your model
    associations and current foreign keys in the database). If there are no
    missing foreign keys, no migration will be created.

Example:
    `rails generate immigration AddMissingForeignKeys`

    If the current date is Apr 1, 2012 and the current time 02:03:04, this
    creates the AddMissingForeignKeys migration
    db/migrate/20120401020304_add_missing_foreign_keys.rb with appropriate
    add_foreign_key calls in the Change migration. If on Rails < 3.1, they
    will be in the Up migration, and corresponding remove_foreign_key calls
    will be in the Down migration.
