rails URLの:idをformで保存したい

URL　/xx/[:id]/yyの[:id]をform_withでdbに保存する方法を教えていただきたいです。ストロングパラメータのmergeやhidden_fieldなどを使いましたが、上手く行きませんでした。

route.rb

Rails.application.routes.draw do
  root 'top_page#index'
  devise_for :users
  resources :calendars do
    resources :calendar_messages, only: [:index, :create, :destroy]
  end
  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
end

コード
class CalendarsController < ApplicationController
    def index
        @calendars = Calendar.all
      end
    
      def new
        @calendar = Calendar.new
      end
    
      def show
        @calendar = Calendar.find(params[:id])
      end
    
      def create
        Calendar.create(calendar_params)
        redirect_to calendars_path
      end
    
      def destroy
        @calendar = Calendar.find(params[:id])
        @calendar.destroy
        redirect_to calendars_path, notice:"削除しました"
      end
    
      def edit
        @calendar = Calendar.find(params[:id])
      end
    
      def update
        @calendar = Calendar.find(params[:id])
        if @calendar.update(calendar_params)
          redirect_to calendars_path, notice: "編集しました"
        else
          render 'edit'
        end
      end
    
      private
    
      def calendar_params
        params.require(:calendar).permit(:title, :content, :start_time)
      end
    
end

コード calendar > show.html.erb
<%= form_with(model: @calendar, local: true) do |form| %>

  <div class="title">
    <%= form.label :title %>
    <%= form.text_field :title %>
  </div>

    <div class="time">
    <%= form.label :start_time %>
    <%= form.datetime_select :start_time %>
  </div>

  <div class="content">
    <%= form.label :content %>
    <%= form.text_field :content %>
  </div>


  <div class="submit">
    <%= form.submit %>
  </div>

  <%= link_to "チャットへ", calendar_calendar_messages_path(@calendar.id) %>
  
<% end %>

コード
class CalendarMessagesController < ApplicationController
  def index
    @messages = CalendarMessage.find_by(calendar_id: params[:id])
    @message = CalendarMessage.new
  end

  def create
    #CalendarMessage.calendar_id = params
    @message = CalendarMessage.new(calendar_message_params)

    if @message.save
      redirect_to calendar_calendar_messages_path
    else
      render calendar_calendar_messages_path
    end
  end

  def destroy
  end

  def calendar_message_params
    params.require(:calendar_message).permit(:message, :calendar_id)
.merge(user_id: current_user.id)
  end
end

コード calendar_messages > index.html.erb
<%= form_with(model: @calendar_message, local: true) do |form| %>
  
  <div class="message">
    <%= form.text_field :message, placeholder: "メッセージを入力" %>
  </div>
  
  <div class="submit">
    <%= form.submit "送信" %>
  </div>
<% end %>