Single/Multi External User Picker
The app also provides two custom field types:
Single External User Picker
Multi External User Picker
Those fields allow you to display related external users on your issue views. To create the custom fields, click on the gear icon. Then, select Issues. On the left sidebar, click on “Custom fields”. Click on the “Create custom field” button.
After adding your field to the associated screens, this is how your end users will see the field when editing.