This function returns a string that contains an at sign symbol (@) and a function call.
The function call returns a system-defined number that identifies the user to whom the work item
is bound.
The @ID corresponds to the ID of the F_BoundUser. F_BoundUser can be used only on a
post-assignment of a single participant step. For a multiparticipant step, the value can be 0, a
random participant, or one of the step participants.
The syntax is as follows:
@+numbertostring(F_BoundUser)