Have some flexibility in "Assign issue" actions.

At the moment, if we select the "Smart Value" option for "Assign Issue" action, the information in the field is matched towards user_key on the app_user table.

With the GDPR compliance efforts, user keys are now in the JIRAUSERXXXXX format. This makes it difficult to use "Smart Values" here.

Would be great if options can be allowed to match with lower_user_name from the same table.