Rails 6.1 Multiple Database Foreign Keys

I want to create a table with a foreign key in a different database.

Is this possible with rails 6.1?

The guide says Rails 6.1 will support using has_many relationships and creating 2 queries instead of joining but it doesn't say how to do it.

My attempt is this;

create_table :comments do |t|
  t.references :post, foreign_key: { to_database: :primary }
  t.uuid :uuid, default: 'uuid_generate_v4()'
  t.timestamps
end