Rails 5 — как динамически (Ajax) добавить элемент на страницу с ассоциацией has_many through не сохраняя его в БД?

Question

[Diesel-nick]

Всем привет!
В Rails 5 приложении сделал 3-и модели:

app/models/user.rb

class User < ApplicationRecord
  has_many :team_users
  has_many :teams, through: :team_users
  accepts_nested_attributes_for :team_users, :teams, allow_destroy: true
end

app/models/team.rb

class Team < ApplicationRecord
  has_many :team_users
  has_many :users, through: :team_users
  accepts_nested_attributes_for :team_users, allow_destroy: true, reject_if: proc { |a| a['user_id'].blank? }
end

app/models/team_user.rb

class TeamUser < ApplicationRecord
  belongs_to :team
  belongs_to :user
  accepts_nested_attributes_for :team, :user, allow_destroy: true
end

app/controllers/teams_controller.rb

class TeamsController < ApplicationController
  before_action :set_team, :set_team_users, only: [:show, :edit, :update, :destroy]
  before_action :set_team_ancestry, only: [:new, :edit, :create, :update, :destroy]
  before_action :set_new_team_user, only: [:new, :edit]
  before_action :logged_in_user
  
  layout 'sidebar'
  
  # GET /teams
  def index
    @teams = Team.search(params[:search], :name).sorting(params[:sort], params[:direction]).paginate(page: params[:page])
  end

  # GET /teams/1
  def show
  end

  # GET /teams/new
  def new
    @team = Team.new(parent_id: params[:parent_id])
  end

  # GET /teams/1/edit
  def edit
    @team_users = @team.team_users
  end

  # POST /teams
  def create
    @team = Team.new(team_params)
    
    respond_to do |format|
      if @team.save
        format.html { redirect_to @team, success: t('.flash.success.message') }
      else
        format.html { render :new, danger: t('.flash.danger.message') }
      end
    end
  end

  # PATCH/PUT /teams/1
  def update
    respond_to do |format|
      if @team.update(team_params)
        format.html { redirect_to @team, success: t('.flash.success.message') }
      else
        format.html { render :edit, danger: t('.flash.danger.message') }
      end
    end
  end

  # DELETE /teams/1
  def destroy
    @team.destroy
    respond_to do |format|
      format.html { redirect_to teams_url, success: t('.flash.success.message') }
    end
  end
  
  private
    # Use callbacks to share common setup or constraints between actions.
    def set_team
      @team = Team.find(params[:id])
    end
    
    def set_team_ancestry
      @team_collection = Team.where.not(id: params[:id]).all.each { |c| c.ancestry = c.ancestry.to_s + (c.ancestry != nil ? "/" : '') + c.id.to_s 
      }.sort{ |x,y| x.ancestry <=> y.ancestry }.map{ |c| ["-" * (c.depth - 1) + c.name,c.id] }
    end
    
    def set_team_users
      @team_users_collection = User.all.collect { |p| [ p.name, p.id ] }
    end
    
    def set_new_team_user
      @team_users_new = @team.team_users.build
    end
    
    # Never trust parameters from the scary internet, only allow the white list through.
    def team_params
      params.require(:team).permit(
        :name,
        :parent_id,
        team_users_attributes: [:_destroy, :id, :user_id]
      )
    end
end

При первом входе на страницу редактирования команды отображаются все пользователи связанные с командой + def set_new_team_user из teams_controller.rb создаёт новый объект team_user.

Как реализовать динамическое добавление пользователей на страницу команды после выбора из селекта и нажатия на кнопку "Add new user"? Но при этом паршл для уже добавленных пользователей - должен быть в виде текста ФИО, а для добавления использовать форму селекта (т.е. Cocoon gem не совсем подходит, там паршалы совпадают) и комит изменения для team_users только после сабмита на основной форме team.

app/views/teams/edit.html.erb