feat: add community container nextcloud-exporter

- allows monitoring your nextcloud with prometheus
- You can create a Dashboard in Grafana to visualize the collected data

Signed-off-by: Benjamin Brahmer <info@b-brahmer.de>

community-containers/nextcloud-exporter/nextcloud-exporter.json

@@ -0,0 +1,37 @@
+{
+    "aio_services_v1": [
+        {
+            "container_name": "nextcloud-aio-nextcloud-exporter",
+            "display_name": "Prometheus Nextcloud Exporter",
+            "documentation": "https://github.com/nextcloud/all-in-one/tree/main/community-containers/nextcloud-exporter",
+            "image": "ghcr.io/xperimental/nextcloud-exporter",
+            "image_tag": "0.8.0",
+            "internal_port": "9205",
+            "restart": "unless-stopped",
+            "depends_on": [
+                "nextcloud-aio-nextcloud"
+            ],
+            "ports": [
+                {
+                  "ip_binding": "%APACHE_IP_BINDING%",
+                  "port_number": "9205",
+                  "protocol": "tcp"
+                }
+            ],
+            "environment": [
+                "TZ=%TIMEZONE%",
+                "NEXTCLOUD_SERVER=https://%NC_DOMAIN%",
+                "NEXTCLOUD_AUTH_TOKEN=%NEXTCLOUD_EXPORTER_TOKEN%",
+                "NEXTCLOUD_LISTEN_ADDRESS=0.0.0.0:9205",
+                "NEXTCLOUD_TIMEOUT=5s",
+                "NEXTCLOUD_TLS_SKIP_VERIFY=true"
+            ],
+            "secrets": [
+                "NEXTCLOUD_EXPORTER_TOKEN"
+            ],
+            "nextcloud_exec_commands": [
+                "php /var/www/html/occ config:app:set serverinfo token --value \"%NEXTCLOUD_EXPORTER_TOKEN%\""
+            ]
+        }
+    ]
+}

community-containers/nextcloud-exporter/readme.md

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+## Prometheus Nextcloud Exporter
+
+A Prometheus exporter that collects metrics from your Nextcloud instance for monitoring and alerting.
+
+### What it does
+- Monitors user activity, file counts, and storage usage
+- Tracks system health, database size, and app statistics  
+- Exposes metrics on port `9205` for Prometheus to scrape
+- Uses Nextcloud's serverinfo API with secure token authentication
+
+### Use cases
+- Monitor Nextcloud performance and capacity
+- Set up alerts for system issues or resource limits
+- Create dashboards showing usage trends and system health
+- Track active users and storage growth over time
+
+### Prometheus Configuration
+Add this to your `prometheus.yml` to scrape the exporter:
+
+```yaml
+scrape_configs:
+  - job_name: 'nextcloud'
+    scrape_interval: 90s
+    static_configs:
+      - targets: ['your-nextcloud-domain.com:9205']
+    metrics_path: /metrics
+    scheme: http
+```
+
+Replace `your-nextcloud-domain.com` with your actual Nextcloud domain.
+
+### Notes
+Automatically configures the required serverinfo token for authentication between Nextcloud and the exporter. 
+
+Compatible with Grafana for visualization (dashboard ID `20716` available).
+
+https://grafana.com/grafana/dashboards/20716-nextcloud/
+
+### Repository
+https://github.com/xperimental/nextcloud-exporter
+
+### Maintainer
+https://github.com/grotax