[WarpFood] Fixed Link in Mattermost Notification for PizzaSheets

www/web/warpfood/views.py

@@ -17,7 +17,7 @@ from datetime import datetime, timedelta
 # ToDo: Username with hidden Field. Maybe insecure
 #
 def get_sheet_link(request, sheet):
-    return request.get_host()+"/pizza/view/"+str(sheet.id)
+    return "https://"+request.get_host()+"/pizza/view/"+str(sheet.id)
 
 def index(request):
     form = FoodSheetForm()