add documentation about disabled apps

Author: cmulk

docs/apps.md

@@ -5,7 +5,9 @@ networking, hardware-in-the-loop devices, etc. in a layered, scripted, and
 codified manner. `phenix` itself includes four (4) default apps that get applied
 to every experiment by default. In addition to the default apps, it is possible
 to apply _user apps_ to an experiment using a
-[scenario](configuration.md#scenario) configuration.
+[scenario](configuration.md#scenario) configuration. Apps can also be disabled at startup,
+either through the `phenix experiment create` command or in the scenario file. This allows apps to execute
+their `running` stage only when manually triggered by the user.
 
 ## Default Apps
 

docs/schema.md

@@ -55,6 +55,11 @@ Scenario:
 			  setting0: true
 			  setting1: 42
 			  setting2: universe key
+		  disabled:
+			type: boolean
+			default: false
+			example: false
+			nullable: true	  
 		  hosts:
 			type: array
 			items:

docs/state-of-health.md

@@ -114,6 +114,7 @@ in detail below.
 spec:
   apps:
   - name: soh
+    disabled: false
     metadata:
       appMetadataProfileKey: sohProfile # metadata key to look for in other apps
       c2Timeout: 5m
@@ -182,6 +183,11 @@ spec:
 
 ### Configuration Options
 
+* `disabled`: Like any (non-default) phenix app, `soh` can be disabled at startup
+  by setting `disabled: true`. In this case, health checks will not be run at experiment
+  startup but can be triggered manually after the experiment is running through either
+  the `phenix` cli or web UI
+
 * `appMetadataProfileKey`: since the listeners and processes one might want to
   monitor could be highly dependent on other apps that are configured for an
   experiment, it's possible to specify the `hostListeners` and `hostProcesses`