[BUG] Simulating a Prometheus Alerts to Teams Channel - results in not found

[AurimasNav]

Describe the bug
trying to test notifications in teams channel with the example json provided in readme results in {"message":"Not Found"}
even though actual alerts are displayed in teams.

Version
docker image 1.5.2
helm chart 1.3.4

To Reproduce
save the example json as file and execute command
curl -X POST -d @prom-alert.json http://localhost:2000/alertmanager

Expected behavior
result representing the validity of msteams configuration, either failure or success, but not a "not found" message without anything posted to the teams while actual alerts are successfully posted there.