Description:
    Generates a new database migration which uses the
    nandi DSL. Supports both single and multi-database
    configurations.

    If no --database option is specified, uses the default database.

Examples:
    rails generate nandi:migration add_stuff_to_things

    This will create:
        db/safe_migrations/20190424123727_add_stuff_to_things.rb

Multi-database examples:
    rails generate nandi:migration add_stuff_to_things --database primary
        creates migration in primary database directory

    rails generate nandi:migration add_analytics_table --database analytics
        creates migration in analytics database directory
