Create Three Symfony Back Ends - Part #4 - Docker for Easy Database

As our various JSON API implementations expect to be able to save and retrieve data beyond the lifetime of a single request, it makes sense that sooner or later, we're going to need a database. Depending on your preference, you may wish to use MySQL, or Postgres for your database. Sometimes one is easier than the other, sometimes it makes no difference. We're going to use Docker for our database. You do not need to. It just makes life easier, in my opinion. Whichever database you want to use, a docker-compose.yml file is going to make working with Docker the easiest it can be.