Add a setup for using docker compose to run a local database

This will prefer a `DATABASE_URL` if it's set, otherwise, fall back
to checking for a running docker database via docker compose, and
only if that fails, fall back to a system postgres server

This adds `dotenv` to the requirements, to avoid duplicating the
authentication credentials for docker's postgres

.postgres.env

@@ -0,0 +1,4 @@
+POSTGRES_USER="rom"
+POSTGRES_PASSWORD="password"
+POSTGRES_DATABASE="rom_factory"
+POSTGRES_HOST_AUTH_METHOD="trust"

Gemfile

@@ -10,11 +10,13 @@ gem "faker", "~> 3.0"
 
 gem "rspec", "~> 3.0"
 
+gem "dotenv"
+
 git "https://github.com/rom-rb/rom.git", branch: "release-5.3" do
-  gem "rom-core"
+  gem "rom"
   gem "rom-changeset"
+  gem "rom-core"
   gem "rom-repository"
-  gem "rom"
 end
 
 group :test do

compose.yml

@@ -0,0 +1,7 @@
+---
+services:
+  db:
+    image: postgres
+    ports:
+      - 5432
+    env_file: .postgres.env

spec/spec_helper.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 require_relative "support/coverage"
+require "dotenv"
+Dotenv.load(".postgres.env", ".env")
 
 require "pathname"
 SPEC_ROOT = root = Pathname(__FILE__).dirname
@@ -18,10 +20,16 @@
 end
 
 DB_URI = ENV.fetch("DATABASE_URL") do
+  auth = ENV.values_at("POSTGRES_USER", "POSTGRES_PASSWORD").join(":")
+  address = `docker compose port db 5432 2> /dev/null`.strip
+  address = [auth, address].join("@") if address
+
+  address ||= "localhost"
+
   if defined? JRUBY_VERSION
-    "jdbc:postgresql://localhost/rom_factory"
+    "jdbc:postgresql://#{address}"
   else
-    "postgres://localhost/rom_factory"
+    "postgres://#{address}"
   end
 end