Issue Summary

Jira should send notification emails to both the previous assignee and the current assignee, whenever the assignee field changes.

Steps to Reproduce

Have 3 users on the site, User A, User B, User C

1. User A creates an issue and Assigned it to User B
2. User A then assigns the issues to User C

Expected Results

User B should be notified that the issue has been unassigned from them. 

Actual Results

Only user C is notified that the issue is assigned to them

Workaround

Currently there is no known workaround for this behaviour. A workaround will be added here when available