Fetch indicators from Intel 471 Indicator Stream feed.

* **TITAN** — Titan API (`api.intel471.com`) for old Titan based indicators.
* **Verity471** — Verity471 API (`api.intel471.cloud`) for Verity471 based indicators.

**Credentials**

* **Username** — API username
* **Password** — API key 
Depends on selected backend:
  * **TITAN:** obtain your API key from [Titan API settings](https://titan.intel471.com/).
  * **Verity471:** request API credentials through the [Intel471 Developer Portal](https://developer.intel471.com/) (organization SSO sign-up / login).

Set **Intel 471 backend** and credentials so they match the same provisioning path (Titan vs Verity471).