Add alertmanager as supported sender and update deps

tests/test_alertmanager.py

@@ -0,0 +1,57 @@
+from ops_bot.alertmanager import prometheus_alert_to_markdown
+import json
+
+payload = json.loads(
+    """
+{
+  "receiver": "matrix",
+  "status": "firing",
+  "alerts": [
+    {
+      "status": "firing",
+      "labels": {
+        "alertname": "InstanceDown",
+        "environment": "monitoring.example.com",
+        "instance": "webserver.example.com",
+        "job": "node_exporter",
+        "severity": "critical"
+      },
+      "annotations": {
+        "description": "webserver.example.com of job node_exporter has been down for more than 5 minutes.",
+        "summary": "THIS IS A TEST Instance webserver.example.com down"
+      },
+      "startsAt": "2022-06-23T11:53:14.318Z",
+      "endsAt": "0001-01-01T00:00:00Z",
+      "generatorURL": "http://monitoring.example.com:9090",
+      "fingerprint": "9cd7837114d58797"
+    }
+  ],
+  "groupLabels": {
+    "alertname": "InstanceDown"
+  },
+  "commonLabels": {
+    "alertname": "InstanceDown",
+    "environment": "monitoring.example.com",
+    "instance": "webserver.example.com",
+    "job": "node_exporter",
+    "severity": "critical"
+  },
+  "commonAnnotations": {
+    "description": "webserver.example.com of job node_exporter has been down for more than 5 minutes.",
+    "summary": "Instance webserver.example.com down"
+  },
+  "externalURL": "https://alert.example",
+  "version": "4",
+  "groupKey": "",
+  "truncatedAlerts": 0
+}"""
+)
+
+
+def test_alertmanager():
+    r = prometheus_alert_to_markdown(payload)
+    assert len(r) == 1
+    plain, formatted = r[0]
+
+    assert "firing" in plain and "Instance webserver.example.com down" in plain
+    assert "firing" in formatted and "Instance webserver.example.com down" in formatted