add docs for monitoring (#44)

Author: vdebergue

docs/thehive/setup/operations/monitoring/grafana-dashboard.jpg

@@ -0,0 +1,81 @@
+# Monitoring TheHive
+
+The monitoring will allow you to get metrics about the behavior of your TheHive instance: request time, cpu and memory usage ...
+
+TheHive uses the library [kamon.io](https://kamon.io/) and by default the monitoring is **disabled**
+
+TheHive ships with the integration for Prometheus reporter. <br> Other reporters are **not** included by TheHive. If you would like to see a reporter included by default in TheHive, contact us.
+
+
+
+![Grafana Dashboard](grafana-dashboard.jpg)
+
+## Metrics setup with Prometheus and Grafana
+
+Here we will setup metrics reporting with [Prometheus](https://prometheus.io/) and [Grafana](https://grafana.com/)
+
+### TheHive configuration
+
+In your `application.conf`, add this section to the configuration:
+
+```
+kamon {
+    # Activate kamon module - disabled by default
+    enabled = true
+
+    # Activate the prometheus reporter
+    modules {
+      prometheus-reporter.enabled = yes
+    }
+
+    environment.tags {
+        # Setup additional tags that will be sent to prometheus 
+        # See https://kamon.io/docs/latest/reporters/prometheus/#sending-environment-tags-to-prometheus
+        # ex: env = prod
+    }
+
+    # Reference: https://kamon.io/docs/latest/reporters/prometheus/#configuration
+    prometheus {
+      include-environment-tags = true
+      # Start and embedded-server on the provided port. 
+      # If using docker, make sure that this port is accessbile
+      embedded-server {
+        hostname = 0.0.0.0
+        port = 9095
+      }
+    }
+}
+```
+
+You will need to restart TheHive for the configuration to take effect
+
+To check that the prometheus reporter is working, connect to <http://THEHIVE:9095/metrics>
+You should see a list of metrics that are reported by TheHive.
+
+
+### Prometheus configuration
+
+Add the [scrape configuration](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#scrape_config) to prometheus configuration `prometheus.yml`
+
+```yaml
+scrape_configs:
+  # ...  other scrape configs 
+
+  - job_name: 'thehive'
+    scrape_interval: 30s
+    static_configs:
+      - targets: ['THEHIVE:9095'] # set the ip or hostname for TheHive
+```
+
+In a dynamic environment like kubernetes, the TheHive service can be automatically discovered by prometheus. You can enable this with labels on your pod or by adding a `PodMonitor` resource. See the adaquate documentation: Prometheus [configuration](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#kubernetes_sd_config) or Prometheus [operator](https://prometheus-operator.dev/docs/user-guides/getting-started/)
+
+
+### Grafana configuration
+
+- Make sure that prometheus is setup as a Datasource inside Grafana
+- Import dashboards or create your own. We recommend the following dashboards (these dashboards were not created by Strangebee):
+    - [Kamon 2.x - API dashboard](https://grafana.com/grafana/dashboards/12317-api-dashboard/): see API metrics like throughoutput, latency, % of error status. *Note that TheHive frontend uses long polling, some requests take 60 seconds and they will appear as outliers in this dashboard*
+    - [Kamon 2.x - System metrics dashboard](https://grafana.com/grafana/dashboards/12315-system-metrics-dashboard/): see info about CPU or memory usage, JVM metrics like Heap usage or GC
+    - [Kamon 2.x - Akka](https://grafana.com/grafana/dashboards/10776-kamon-akka-marcelo/): info about Akka system, actors, processing time
+
+    To make these dashboards work, you may need to edit the dashboard variables 

docs/thehive/setup/operations/monitoring/monitoring.md

@@ -111,6 +111,7 @@ nav:
         - thehive/setup/operations/fail2ban.md
         - thehive/setup/operations/change-index.md
         - thehive/setup/operations/troubleshooting.md
+        - thehive/setup/operations/monitoring/monitoring.md
     - 'Administration Guides': 
       - 'First start': thehive/administration/first-start.md
       - 'Manage organisations':