apollo-client-config-data/src/main/java/com/ctrip/framework/apollo/config/data/extension/properties/ApolloClientExtensionProperties.java/ApolloClientExtensionProperties/toString
class ApolloClientExtensionProperties:  @Override
  public String toString() {
    return "ApolloClientExtensionProperties{" +
        "enabled=" + enabled +
        ", messagingType=" + messagingType +
        '}';
  }