Correctly identify zulip-terminal in login notification e-mails

### Description of feature missing from another Zulip client When logging in to chat.zulip.org from other Zulip clients, I get notification e-mails like: - **Subject:** New login from Zulip on Android **Body** including "Device: Zulip on Android." - **Subject:** New login from Zulip on Linux etc. When I log in to `zulip-term`, I also receive an e-mail, but it looks like: - **Subject:** New login from An unknown browser on an unknown operating system **Body** including "Device: An unknown browser on an unknown operating system." It would be nice if this e-mail correctly identified zulip-terminal, or at least didn't say "unknown browser", as the terminal app is not a browser. Maybe this has to do with the terminal app sending a HTTP User-Agent: header with its initial API requests? ### When was this feature first available in Zulip? If you know: - **Zulip version:** Zulip Cloud today - **Zulip feature level:** ?