apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/controller/EnvController.java/EnvController/envs
class EnvController:  @GetMapping
  public List<String> envs() {
    List<String> environments = new ArrayList<>();
    for(Env env : portalSettings.getActiveEnvs()) {
      environments.add(env.toString());
    }
    return environments;
  }