apollo-openapi/src/main/java/com/ctrip/framework/apollo/openapi/client/ApolloOpenApiClient.java/ApolloOpenApiClient/ApolloOpenApiClient
class ApolloOpenApiClient:  private ApolloOpenApiClient(String portalUrl, String token, RequestConfig requestConfig) {
    this.portalUrl = portalUrl;
    this.token = token;
    CloseableHttpClient client = HttpClients.custom().setDefaultRequestConfig(requestConfig)
        .setDefaultHeaders(Lists.newArrayList(new BasicHeader("Authorization", token))).build();

    String baseUrl = this.portalUrl + ApolloOpenApiConstants.OPEN_API_V1_PREFIX;
    appService = new AppOpenApiService(client, baseUrl, GSON);
    clusterService = new ClusterOpenApiService(client, baseUrl, GSON);
    namespaceService = new NamespaceOpenApiService(client, baseUrl, GSON);
    itemService = new ItemOpenApiService(client, baseUrl, GSON);
    releaseService = new ReleaseOpenApiService(client, baseUrl, GSON);
  }