Issue Summary

Unable to set user with special symbols in user identifier (user_name in DB) in a custom field of type User Picker (multiple users)

Steps to Reproduce

1. User has special symbols in user identifier
2. Setting the value to this user in a custom field of type User Picker (multiple users) fails with error: 
   _"Pick another user as the selected user doesn’t exist."_
3. The operation works in the old issue view but fails in the new view
4. Also, the same operation might fail via REST API too

{"errorMessages":[],"errors":{"customfield_xxx":"Pick another user as the selected user doesn’t exist."}}

Expected Results

Operation to work

Actual Results

The operation fails with error: "Pick another user as the selected user doesn’t exist."

Workaround

Use the old issue view, or contact support to have the value corrected