Update docker compose to use unified db container

pg-init-scripts/create-multiple-databases.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+
+# Script taken with modifications from https://dev.to/bgord/multiple-postgres-databases-in-a-single-docker-container-417l
+
+set -e
+set -u
+
+function create_user_and_database() {
+	local database=$1
+	echo "  Creating user and database '$database'"
+	psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" <<-EOSQL
+	    CREATE DATABASE "$database";
+	    GRANT ALL PRIVILEGES ON DATABASE "$database" TO "$POSTGRES_USER";
+EOSQL
+}
+
+for var in $(env | grep '^POSTGRES_CREATE_DB_' | awk -F '=' '{print $2}'); do
+	echo "Creating database: $var"
+	create_user_and_database $var
+done