Add system context diagram to design package

src/main/asciidoc/models/design/systemContextDiagram.puml

@@ -0,0 +1,13 @@
+@startuml
+
+:unauthenticated user\n(person): as UU
+:customer\n(person): as K
+:Hannes Wurst, administrator\n(person): as A
+
+usecase (Cateringservice\n[Softwaresystem]\nan online software for planning a catering event) as Use
+
+UU ---> Use: login as customer\nor administrator,\nregister as new customer,\nview catalog
+K ---> Use: plan a \ncatering event
+A ---> Use: remove customers,\nmanage inventory/staffs
+
+@enduml