Part 1 of this fix. The currentSelection will be null when editing an existing entry. We are not sending the cleared out contact/ticket/opp values if the account is changed, which is a TODO.
#MBL-10452
Allow applyTo to be a custom function so a field can have complete control over the payload's value. Clearing lookups with applyTo set was not working otherwise.
#MBL-10452
Update comment.