prevent dragging for anonymous user on taskboard

app/coffee/modules/taskboard/sortable.coffee

@@ -36,6 +36,11 @@ module = angular.module("taigaBacklog")
 
 TaskboardSortableDirective = ($repo, $rs, $rootscope) ->
     link = ($scope, $el, $attrs) ->
+        bindOnce $scope, "project", (project) ->
+            # If the user has not enough permissions we don't enable the sortable
+            if not (project.my_permissions.indexOf("modify_us") > -1)
+                return
+
             oldParentScope = null
             newParentScope = null
             itemEl = null