Proposal

Trying to send a 'DeadManSwitch' alert to OpsGenie, however they expect a different Authorization header than what we can send via webhook

They expect Authorization GenieKey <api-key>, prometheus currently sends Authorization Bearer <api-key> when using the bearer_token setting in http_config

Bug Report

What did you do?
Tried to configure DeadManSwitch / Heartbeat for OpsGenie using Webhooks + HTTP Config

What did you expect to see?
Webhook successs

What did you see instead? Under which circumstances?
HTTP 401 error because of headers issue as stated

Environment

• Prometheus version: 2.3.1

• Alertmanager version: 0.15.0