Feature/implement traefik documentation (#628)

* Write documentation for Traefik integration

* Typo fix

* technologie > technology

* Fix according to @dunglas review

Author: Darkweak

deployment/traefik.md

@@ -0,0 +1,122 @@
+# Implement Traefik Into API Platform Dockerized
+
+## Basic Implementation
+
+[Traefik](https://traefik.io) is a reverse proxy / load balancer that's easy, dynamic, automatic, fast, full-featured, open source, production proven, providing metrics, and integrating with every major cluster technology.
+
+This tool will help you to define your own routes for your client, api and more generally for your containers.
+
+Use this custom API Platform `docker-compose.yml` file which implements ready-to-use Traefik container configuration.  
+Override ports and add labels to tell Traefik to listen the routes mentionned and redirect routes to specified container.
+
+
+`--api` Tell Traefik to generate a browser view to watch containers and IP/DNS associated easier  
+`--docker` Tell Traefik to listen docker api  
+`--docker.domain=localhost` The main DNS will be on localhost  
+`labels:` Key for Traefik configuration into Docker integration  
+```yaml
+services:
+#  ...
+  api:
+    labels: 
+      - "traefik.frontend.rule=Host:api.localhost"
+``` 
+The api DNS will be specified with `traefik.frontend.rule=Host:your.host` (here api.localhost)  
+
+`--traefik.port=3000` Port specified to Traefik will be exopsed by container (here React app expose the 3000 port)  
+
+
+```yaml
+version: '3.4'
+
+services:
+  reverse-proxy:
+    image: traefik
+    command: --api --docker --docker.domain=localhost
+    ports:
+      - "80:80" #All HTTP access will be caught by Traefik
+      - "8080:8080" #Access Traefik webview
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+
+  php:
+    image: ${CONTAINER_REGISTRY_BASE}/php
+    build:
+      context: ./api
+    depends_on:
+      - db
+    env_file:
+      - ./api/.env
+    # Comment out these volumes in production
+    volumes:
+      - ./api:/srv/api:rw,cached
+      # If you develop on Linux, uncomment the following line to use a bind-mounted host directory instead
+      # - ./api/var:/srv/api/var:rw
+
+  api:
+    image: ${CONTAINER_REGISTRY_BASE}/nginx
+    labels:
+      - "traefik.frontend.rule=Host:api.localhost"
+    build:
+      context: ./api
+    depends_on:
+      - php
+    # Comment out this volume in production
+    volumes:
+      - ./api/public:/srv/api/public:ro
+
+  db:
+    # In production, you may want to use a managed database service
+    image: postgres:9.6-alpine
+    labels:
+      - "traefik.frontend.rule=Host:db.localhost"
+    environment:
+      - POSTGRES_DB=api
+      - POSTGRES_USER=api-platform
+      # You should definitely change the password in production
+      - POSTGRES_PASSWORD=!ChangeMe!
+    volumes:
+      - db-data:/var/lib/postgresql/data:rw
+      # You may use a bind-mounted host directory instead, so that it is harder to accidentally remove the volume and lose all your data!
+      # - ./docker/db/data:/var/lib/postgresql/data:rw
+    ports:
+      - "5432:5432"
+
+  client:
+    # Use a static website hosting service in production
+    # See https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/template/README.mddeployment
+    image: ${CONTAINER_REGISTRY_BASE}/client
+    build:
+      context: ./client
+    env_file:
+      - ./client/.env
+    volumes:
+      - ./client:/usr/src/client:rw,cached
+      - /usr/src/client/node_modules
+    expose:
+      - 3000
+    labels:
+      - "traefik.port=3000"
+      - "traefik.frontend.rule=Host:localhost"
+
+volumes:
+  db-data: {}
+```
+
+Don't forget the db-data, then database won't work in this dockerized solution.
+
+`localhost` is a reserved domain referred in your `/etc/hosts`. 
+If you want to implement custom DNS such as production DNS in local, just put them at the end of your `/etc/host` file like that: 
+
+```
+# /etc/hosts
+# ...
+
+127.0.0.1       your.domain.com
+```
+
+If you do that, you'll have to update the `CORS_ALLOW_ORIGIN` environment variable `api/.env` to accept the specified URL.
+
+## Known Issues
+
+If your network is of type B, it may conflict with the traefik sub-network.