Add some documentation on monitor_postgrest state

README.md

@@ -108,6 +108,12 @@ Installs the [nginx_status](https://checkmk.com/cms_check_nginx_status.html) age
 
 Install the [php_fpm_pools](https://exchange.checkmk.com/p/php-fpm) agent plugin.
 
+### `checkmk.debian.monitor_postgrest`
+
+Installs the `monitor-postgrest` agent local check.
+Relies on pillar configuration for [postgrest-formula](https://lab.it.hs-hannover.de/salt/postgrest-formula).
+Specifically, if no PostgREST instance defines `admin-server-port` in its configuration the state will ensure that the local check is not present.
+
 ### `checkmk.debian.radsec`
 
 Installs the radsec plugin.