Rails无法保存未选中的复选框

<%= form_with(model: @user) do |form| %>
  <%= form.check_box :admin %>
  <%= form.label :admin, "Admin" %>
  <%= form.submit %>
<% end %>

class UsersController < ApplicationController
  def create
    user_params = user_params_with_defaults
    @user = User.new(user_params)
    if @user.save
      redirect_to @user, notice: 'User was successfully created.'
    else
      render :new
    end
  end

  def update
    user_params = user_params_with_defaults
    @user = User.find(params[:id])
    if @user.update(user_params)
      redirect_to @user, notice: 'User was successfully updated.'
    else
      render :edit
    end
  end

  private

  def user_params_with_defaults
    params[:user][:admin] ||= false
    params.require(:user).permit(:name, :email, :admin)
  end
end

<%= form_with(model: @user, id: 'user_form') do |form| %>
  <%= form.check_box :admin %>
  <%= form.label :admin, "Admin" %>
  <%= form.submit %>
<% end %>

<script>
  document.getElementById('user_form').addEventListener('submit', function() {
    var adminCheckbox = document.querySelector('input[name="user[admin]"]');
    if (!adminCheckbox.checked) {
      var hiddenField = document.createElement('input');
      hiddenField.type = 'hidden';
      hiddenField.name = 'user[admin]';
      hiddenField.value = '0';
      this.appendChild(hiddenField);
    }
  });
</script>