Change job priority on queue page

modules/webapp/src/main/elm/Data/Priority.elm

@@ -2,6 +2,7 @@ module Data.Priority exposing
     ( Priority(..)
     , all
     , fromString
+    , next
     , toName
     )
 
@@ -38,6 +39,16 @@ toName lang =
             "High"
 
 
+next : Priority -> Priority
+next prio =
+    case prio of
+        High ->
+            Low
+
+        Low ->
+            High
+
+
 all : List Priority
 all =
     [ Low, High ]