add dependencies and incorporate env vars into docker-compose file

docker-compose.yml

@@ -3,14 +3,27 @@ services:
   db:
     container_name: buildingmotif-db
     image: postgres
+    environment:
+       - POSTGRES_DB=${POSTGRES_DB}
+       - POSTGRES_USER=${POSTGRES_USER}
+       - POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
     ports:
       - target: 5432
         published: 5432
         protocol: tcp
         mode: host
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready", "-d", "db_prod"]
+      interval: 30s
+      timeout: 30s
+      retries: 5
+      start_period: 10s
 
   api:
     container_name: buildingmotif-api
+    depends_on: # require that the db is up and listening
+      db:
+        condition: service_healthy
     build: .
     image: buildingmotif-api:latest
     ports:
@@ -22,6 +35,8 @@ services:
 
   app:
     container_name: buildingmotif-app
+    depends_on: # require that the api server has started
+      - api
     build: ./buildingmotif-app
     image: buildingmotif-app:latest
     ports: