Email API authentication: keys and sender addresses

Authenticate, then find the addresses you can send from.

1. Open Developers → API keys in IotaBot and create a key with messages:send and messages:read.
2. Keep it on your server as IOTABOT_API_KEY. Send it as Authorization: Bearer ….
3. Use a test key (ib_test_…) while you build — same API, nothing is ever sent.

curl -X GET "https://api.iotabot.com/v1/email/senders" \
  -H "Authorization: Bearer $IOTABOT_API_KEY"

{
  "data": {
    "items": [
      {
        "address": "support@acme.com",
        "website_id": "6a4b3fbbe291bce5bf701c5c",
        "domain": "acme.com",
        "can_send": true
      }
    ]
  }
}