Add prometheus page to how-to (#542)

* add prometheus page to how-to

* add link to server profile example

docs/how-to/prometheus.md

@@ -0,0 +1,10 @@
+---
+title: PingDirectory Metrics with Prometheus
+---
+# Enabling PingDirectory Metrics with Prometheus
+
+In the past, enabling metrics for PingDirectory required a manual process to setup the **statsd** configuration to enable the data to be made available to Prometheus. However, PingDirectory now includes an HTTP servlet extension that can be enabled to expose metrics in Prometheus format.
+
+You can refer to the [documentation](https://docs.pingidentity.com/r/en-us/pingdirectory-92/pd_ds_monitor_server_metrics_prometheus) for the `dsconfig` commands to enable the Prometheus metrics.  The link above is for PingDirectory 9.2, but the process is the same for newer versions.
+
+These `dsconfig` commands can be included in a server profile to ensure that the configuration is applied when the server is started. See [here](https://github.com/pingidentity/pingidentity-server-profiles/blob/master/monitoring/pingdirectory/jolokia/pd.profile/dsconfig/15-prometheus.dsconfig) for an example.

mkdocs.yml

@@ -134,6 +134,7 @@ nav:
                             - ENV Substitution: "how-to/profilesSubstitution.md"
                             - Installing Extensions with PingData Profiles: "how-to/profilesPingDataExtensions.md"
                             - Private Github Repos: "how-to/privateRepos.md"
+                  - PingDirectory and Prometheus: "how-to/prometheus.md"
                   - Vault/Secrets: "how-to/usingVault.md"
                   - Securing the Containers: "how-to/secureContainers.md"
                   - Upgrading Deployments: