updated diagrams and gitignore

docs/architecture-class-diagram.puml

@@ -142,6 +142,15 @@ package "Utils" #DDA0DD {
         ' +hash()
         ' +compare()
     }
+
+    class RecurrenceExpander {
+        ' +expandRecurringEvents()
+    }
+
+    class EventFormatters {
+        ' +getWeeksOverview()
+        ' +getMonthOverview()
+    }
 }
 
 ' Controller -> Service
@@ -161,4 +170,8 @@ EventService --> EventRepository
 AuthService --> JWT
 AuthService --> Password
 
+' Event/Chat uses Utils
+EventService --> RecurrenceExpander
+ChatService --> EventFormatters
+
 @enduml