Support Grafana v9.x messages, fixes #29

tests/example_grafana_9x.json

@@ -0,0 +1,41 @@
+{
+    "receiver": "",
+    "status": "firing",
+    "alerts": [
+        {
+            "status": "firing",
+            "labels": {
+                "alertname": "TestAlert",
+                "instance": "Grafana"
+            },
+            "annotations": {
+                "summary": "Notification test"
+            },
+            "startsAt": "2022-09-07T15:00:26.722304913+02:00",
+            "endsAt": "0001-01-01T00:00:00Z",
+            "generatorURL": "",
+            "fingerprint": "57c6d9296de2ad39",
+            "silenceURL": "https://grafana.example.com/alerting/silence/new?alertmanager=grafana&matcher=alertname%3DTestAlert&matcher=instance%3DGrafana",
+            "dashboardURL": "",
+            "panelURL": "",
+            "valueString": "[ metric='foo' labels={instance=bar} value=10 ]"
+        }
+    ],
+    "groupLabels": {},
+    "commonLabels": {
+        "alertname": "TestAlert",
+        "instance": "Grafana"
+    },
+    "commonAnnotations": {
+        "summary": "Notification test"
+    },
+    "externalURL": "https://grafana.example.com/",
+    "version": "1",
+    "groupKey": "{alertname=\"TestAlert\", instance=\"Grafana\"}2022-09-07 15:00:26.722304913 +0200 CEST m=+246580.963796811",
+    "truncatedAlerts": 0,
+    "orgId": 1,
+    "title": "[FIRING:1]  (TestAlert Grafana)",
+    "state": "alerting",
+    "message": "**Firing**\n\nValue: [ metric='foo' labels={instance=bar} value=10 ]\nLabels:\n - alertname = TestAlert\n - instance = Grafana\nAnnotations:\n - summary = Notification test\nSilence: https://grafana.example.com/alerting/silence/new?alertmanager=grafana&matcher=alertname%3DTestAlert&matcher=instance%3DGrafana\n",
+    "key": "ak"
+}