Add workflow "pre-function" as well as post function

I am sure I have seen a very similar request already, but I can't find it anywhere so sorry if this is a duplicate. We are finding the workflow system very limiting when it comes to setting the assignee of an issue. Sometimes users need the ability to override the default assignee. You are stuck with either having to go with whomever the system tells you (and without extensions that capability is very limited (in particular because of JRA-5496)), or having to select from a list of all assignable users.

There are several ways to address this issue:

• Make workflow assignement conditional: only use the workflow to set the assignee when a user doesn't select "automatic or unassigned".
• Better: provide a pre-workflow function. This gives users the option to set the assignee before the transition screen appears. So for example, set the assignee to the reporter when an issue is resolved so that the reporter appears in the Resolved Issue screen, but give the user the opportunity to change that selection.