Has and belongs to many though option not scoping as expected

I followed the example of the Has and belongs to many. What I was expecting to happen is that when the following code is run, it would scope by the association.

account = Account.first
ActsAsTenant.current_tenant = account
User.where(email: "user@acount.com").first

The idea being the user could belong to many accounts but would only be found if the current_tenant was an account it was a member of.

When I run the above code the query it looks for an account_id on the User model. Producing an error when it can't find the foreign key.

PG::UndefinedColumn: ERROR:  column users.account_id does not exist (ActiveRecord::StatementInvalid)
LINE 1: SELECT "users".* FROM "users" WHERE "users"."account_id" = $...

This is what I expected as the normal behaviour for acts_as_tenant :account. I thought adding the through: option would then allow for the user to belong to many accounts, but only return the one that is the current tenant.

What exactly does the through: option allows for?
Is there a common approach or best practice for a user belonging to many tenants?

Here is the code I used for the models

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :validatable

  has_many :account_users
  acts_as_tenant :account, through: :account_users
end

class AccountUser < ApplicationRecord
  belongs_to :user
  acts_as_tenant :account
end

class Account < ApplicationRecord
  has_many :account_users
  has_many :users, through: :account_users

  validates :name, presence: true, uniqueness: true
  validates :subdomain, presence: true, uniqueness: true
end

Got the same error.

I think it's probably because of this line:

belongs_to tenant, **valid_options

acts_as_tenant/lib/acts_as_tenant/model_extensions.rb

Line 16 in a05d9a2

belongs_to tenant, **valid_options

It doesn't have any has_many association, only belongs_to