feat: connect containers to custom network

- Export the `get` function in `utils/env.js`
- Change the Docker image in `docker.js` from `ubuntu` to `lancatlin/quest-helloworld`
- Remove the `createContainer` and `getContainer` functions from `docker.js`
- Add a `network` constant in `docker.js` that gets the Docker network from the config
- Connect the container to the network in `getOrCreateContainer` function in `docker.js`
- Add `API_ENDPOINT` environment variable in the `attachContainer` function in `docker.js`

Signed-off-by: wancat <wancat@wancat.cc>

server/src/config.js

@@ -1,14 +1,9 @@
-function get(key, defaultValue) {
-  const value = process.env[key]
-  if (value != null) {
-    return value
-  }
-  return defaultValue
-}
+import { get } from './utils/env.js'
 
 export default {
   host: get('HOST', 'localhost'),
   port: get('PORT', 3000),
   db: get('MONGO_URL', 'mongodb://localhost:27017/odyssey-test'),
   jwtSecret: get('JWT_SECRET', 'secret'),
+  dockerNetwork: get('DOCKER_NETWORK', 'linux-odyssey-players'),
 }