Closes #47593.

# Assuming "carts" table has "(shop_id, id)" as a primary key.

add_foreign_key(:orders, :carts, primary_key: [:shop_id, :id])
# or
add_foreign_key(:orders, :carts, column: [:cart_shop_id, :cart_id])

remove_foreign_key(:orders, :carts, primary_key: [:shop_id, :id])
foreign_key_exists?(:orders, :carts, primary_key: [:shop_id, :id])

We discussed 3 possible ways of using add_foreign_key.

The first one (add_foreign_key :brochures, :cars) (no :column and :primary_key options) turned out to be complex to implement, as it introduced a lot of kinda ugly changes in many places because we needed to properly generate these column names (consider configured table name prefixes and suffixes, pass a connection around to be able to query a primary key for the to_table. Some classes, like ForeignKeyDefinition does not have access to the connection, and so we needed to calculate these columns at several places differently and pass there).

And the biggest problem is when we need to add a foreign key for a self referencing tables, like

So I made that it is required to pass at least one of :column or :primary_key options, as it is easy to infer one from the other.

cc @eileencodes @nvasilevski