MongoId - Reference association not working - Rails 7

Question

I have a Rails 7 app where my registration form only contains 2 fields:

• Company Name
• Email

The registration involves the following models:

• Company
• Account
• User

The associations involved are:

• A company has one account (embedded association),
• And an account can have one or multiple users (referenced association)

The idea is that upon registering, the controller should create:

• a Company document created with the name from the form, and embed the Account document
• an Account document, embedded in Company, with a Users Array referencing the user created
• a User document created with the email used in the registration form.

Everything works as expected so far except the Users reference association. Regardless of what I try, the Account document embedded in the Company document does not show a users array with references to my User.

I might be missing something obvious, but I can't see the forest for the trees anymore.

RegistrationsController

    def create
      @account, @user, @company = Account.new, User.new, Company.new
      @user.email = registration_params[:user][:email]
      @account.users << @user
      @company.name, @company.account = registration_params[:company][:name].squish, @account
      
      puts "registration valid checks"
      puts @company.valid?, @account.valid?, @user.valid? #All valid

      if @user.save and @account.save and @company.save
        flash[:email] = @user.email
        redirect_to "/thank-you", notice: "Account was successfully created."
      else
       render :new, status: :unprocessable_entity 
      end
    end

Account Model

class Account
  include Mongoid::Document
  include Mongoid::Timestamps
  
  field :creation_date, type: DateTime

  has_many :users

  embedded_in :company

  validates_presence_of :users, on: :create #Does not yield errors

end

User Model

class User
  include Mongoid::Document
  include Mongoid::Timestamps

  field :email, type: String

  belongs_to :account
  
  validates :email, presence: true, uniqueness:  { case_sensitive: false }, on: :create
end

And yet, when looking at the Company document saved in Mongo, the output looks like this:

[...]
name: 'xxx',
account: {
_id: xxx,
updated_at: xxx,
created_at: xxx
}
[...]

Where I would expect something along the lines of:

[...]
name: 'xxx',
account: {
_id: xxx,
updated_at: xxx,
created_at: xxx,
users: [{_id:'xxxx'}]
}
[...]

Any help would be massively appreciated.

Thanks