Micrometer: add shinyproxy_realm tag

Author: LEDfan

src/main/java/eu/openanalytics/containerproxy/service/IdentifierService.java

@@ -64,7 +64,7 @@ public class IdentifierService {
     public String instanceId = null;
 
     /**
-     * String identifying the realm ShinyProxy operatores in.
+     * String identifying the realm ShinyProxy operates in.
      */
     public String realmId = null;
 

src/main/java/eu/openanalytics/containerproxy/stat/impl/MicrometerRegistryConfiguration.java

@@ -71,7 +71,8 @@ public String tagKey(@NonNull String key) {
                     }
                 })
                 // add a common tag with the instanceId of this server. (it cannot simple be called instance, since that is already a default Prometheus label).
-                .commonTags("shinyproxy_instance", identifierService.instanceId);
+                .commonTags("shinyproxy_instance", identifierService.instanceId,
+                            "shinyproxy_realm", identifierService.realmId != null ? identifierService.realmId : "");
     }