feat(views)!: move task position handling to its own crud entity

BREAKING CHANGE: the position of tasks now can't be updated anymore via the task update endpoint. Instead, there is a new endpoint which takes the project view into account as well.

pkg/models/kanban.go

@@ -201,7 +201,7 @@ func GetTasksInBucketsForView(s *xorm.Session, view *ProjectView, opts *taskSear
 	opts.sortby = []*sortParam{
 		{
 			orderBy: orderAscending,
-			sortBy:  taskPropertyKanbanPosition,
+			sortBy:  taskPropertyPosition,
 		},
 	}