Add PSA Wf Management (#757)

src/docs/PSA/PSAUserGuide.adoc

@@ -17,6 +17,10 @@ include::references/Definition.adoc[]
 
 include::references/Standard_Transitions.adoc[]
 
+=== Service Execution
+
+include::references/Service_Execution.adoc[]
+
 == PSA Portal
 
 === Overall View

src/docs/PSA/references/Service_Execution.adoc

+PSA services can be instantiated in two different ways:
+
+1- Via the <<_psa_portal,ProActive Service Automation>> (PSA) Portal.
+
+2- Via standard workflows (also called *Management Workflows*). ProActive includes predefined standard workflows that manage PSA service lifecycles (e.g., launch and stop PSA services).
+These workflows are provided in the bucket *Service_Automation* under the project *Service Automation - Management*. Their names are constructed using the pattern *PSA_Service_Name* followed by the suffix *_Service*.
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