====== Proxy to Back-end For Development ======
  - Create a file call ''proxy.conf.json'' in the root directory of your project.
  - Fill the config in ''proxy.conf.json'': <code>
  {
  "/BACKEND_SERVER_URL/*": {
    "target": "http://localhost:8080/BACKEND_SERVER_URL/",
    "secure": false,
    "logLevel": "debug",
    "changeOrigin": false,
    "pathRewrite": {
        "^/BACKEND_SERVER_URL": ""
    }
    , "headers": {"ipaddress":"127.0.0.1"}
  }
}
</code>
  - Start your back-end server. Assume your back-end server url is ''http://localhost:8080/BACKEND_SERVER_URL/''
  - Start the front-end with: <code>ng s --base-href /YOUR_BASE_URL/ --deploy-url /BACKEND_SERVER_URL/ --proxy-config proxy.conf.json</code>
  - Now your front-end http request will automatically redirect by angular from port 4200 to 8080 with the relative back-end url.