如何使用ActiveRecord将一个表中的两列指向另一个表中的同一列？

class User< ApplicationRecord
  has_many :posts
end

class Post< ApplicationRecord
  belongs_to :user
end

class AddUserIdToPosts< ActiveRecord::Migration[6.1]
  def change
    add_column :posts, :user_id, :integer
  end
end

rails db:migrate

class User< ApplicationRecord
  has_many :posts
end

class Post< ApplicationRecord
  belongs_to :user
end

user = User.find(1)
posts = user.posts

post = Post.find(1)
user = post.user