feat: add /alertmanager endpoint as Alertmanager -> Apprise bridge

Reuses the same notification path as /crowdsec: formats the
Alertmanager webhook payload (firing/resolved, severity, instance,
summary/description) and forwards it to APPRISE_URL as {title, body}.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -51,6 +51,21 @@ headers:
   Content-Type: application/json
 ```
 
+## Configuration Alertmanager
+
+Sert aussi de pont entre Alertmanager et Apprise (le `webhook_configs` d'Alertmanager
+n'a pas de templating de payload, il envoie son format natif tel quel).
+
+Dans `alertmanager.yml` :
+
+```yaml
+receivers:
+  - name: 'apprise-notifications'
+    webhook_configs:
+      - url: 'http://crowdsec-notify:5000/alertmanager'
+        send_resolved: true
+```
+
 ## Auteur
 
 Maxime Killinger

app.py

@@ -111,6 +111,74 @@ def handle_crowdsec():
         logger.exception(f"Error processing CrowdSec alert: {e}")
         return jsonify({"status": "error", "message": str(e)}), 500
 
+@app.route('/alertmanager', methods=['POST'])
+def handle_alertmanager():
+    try:
+        data = request.json or {}
+        alerts = data.get("alerts", [])
+        if not alerts:
+            logger.debug("Received empty Alertmanager payload")
+            return jsonify({"status": "no data"}), 200
+
+        def format_alert(alert):
+            labels = alert.get("labels", {})
+            annotations = alert.get("annotations", {})
+            name = labels.get("alertname", "alerte")
+            severity = labels.get("severity", "")
+            instance = labels.get("instance") or labels.get("container") or labels.get("job") or ""
+
+            head = name
+            if severity:
+                head += f" [{severity}]"
+            if instance:
+                head += f" — {instance}"
+
+            out = [head]
+            summary = annotations.get("summary")
+            description = annotations.get("description")
+            if summary:
+                out.append(f"   {summary}")
+            if description and description != summary:
+                out.append(f"   {description}")
+            return "\n".join(out)
+
+        firing = [a for a in alerts if a.get("status") == "firing"]
+        resolved = [a for a in alerts if a.get("status") == "resolved"]
+
+        lines = []
+        if firing:
+            lines.append(f"🔥 {len(firing)} alerte(s) active(s)")
+            lines.extend(format_alert(a) for a in firing)
+        if resolved:
+            if lines:
+                lines.append("")
+            lines.append(f"✅ {len(resolved)} résolue(s)")
+            lines.extend(format_alert(a) for a in resolved)
+
+        status = data.get("status", "firing")
+        group_name = data.get("groupLabels", {}).get("alertname", "")
+        title = ("🔥" if status == "firing" else "✅") + " Alertmanager"
+        if group_name:
+            title += f" — {group_name}"
+
+        body = "\n".join(lines).strip()
+
+        # Send to Apprise
+        response = requests.post(APPRISE_URL, json={"title": title, "body": body}, timeout=10)
+
+        if response.ok:
+            logger.info(f"Alertmanager notification sent: {len(firing)} firing, {len(resolved)} resolved")
+        else:
+            logger.error(f"Apprise error: {response.status_code} - {response.text}")
+            return jsonify({"status": "error", "code": response.status_code}), 502
+
+        return jsonify({"status": "sent", "firing": len(firing), "resolved": len(resolved)}), 200
+
+    except Exception as e:
+        logger.exception(f"Error processing Alertmanager alert: {e}")
+        return jsonify({"status": "error", "message": str(e)}), 500
+
+
 @app.route('/health', methods=['GET'])
 def health():
     return jsonify({"status": "ok"}), 200