Overview: We use a third party docker image called prometheus-mstreams. It's a lightweight go application that pushes to our Microsoft teams via a webhook.
There is little to no setup for this application to work. All of the setup is completed via the Kubernetes deployment file (ie '../deploy/K8-Blue/prom2teams.yml') and the alert-manager config file (ie '../docker/alert-manager/alert-conf-blue.yml'). It pushes all notification via a webhook that it curls an alert to.