build: use environment variables in docker-compose

docker-compose.yml

@@ -2,12 +2,14 @@ version: '3.1'
 
 services:
   web:
+    image: breccia-mapper
     build: .
     ports:
       - 8000:8000
     environment:
-      DEBUG: "true"
+      DEBUG: ${DJANGO_DEBUG}
       DATABASE_URL: sqlite:////app/db.sqlite3
+      SECRET_KEY: ${DJANGO_SECRET_KEY}
     volumes:
       - ./db.sqlite3:/app/db.sqlite3:z
       - static_files:/app/static
@@ -18,6 +20,8 @@ services:
     ports:
       - 80:80
       - 443:443
+    environment:
+      CADDY_TLS_EMAIL: ${CADDY_TLS_EMAIL}
     volumes:
       - ./Caddyfile:/etc/caddy/Caddyfile:z
       # Caddy serves static files collected by Django