Build docker compose file

Docker
#1

Gents,
First of all, I’d like to thank you for the useful course. I have a development project that I’m working. the project is consist of 3 tiers web(nginx), App (odoo) and DB(postgres). at first I have created docker compose file for the app and the database. they are some customization being done on the app using paython. Now, I need to configure nginx for reverse proxy and add it to the docker-compose file. So can you help me in this one. for future use how can i have a docker file to ease the implementation.

version: '2'
services:
  app:
    image: odoo:12.0
    depends_on:
      - db
    ports:
      - "8069:8069"
    volumes:
      - odoo-app-data:/var/lib/odoo
      - ./config:/etc/odoo
      - ./addons:/mnt/extra-addons
  db:
    image: postgres:10
    environment:
      - POSTGRES_DB=postgres
      - POSTGRES_PASSWORD=odoo
      - POSTGRES_USER=odoo
      - PGDATA=/var/lib/postgresql/data/pgdata
    volumes:
      - odoo-db-data:/var/lib/postgresql/data/pgdata
volumes:
  odoo-app-data:
  odoo-db-data: