Summary

Editing a multi-user picker field for an issue via */rest/api/3/issue/

* containing the following JSON body where custom field ID is for a multi-user picker type field:

{
    "fields": {
        "customfield_10055": [
            {
                "accountId": "0f0000fff0ffff0f0000f00f"
            }
        ]
    }
}

1. Get HTTP response code 204.
2. Check the issue in the Jira UI.

Expected Results

The multi-user picker custom field has been updated to include the specified user.

Actual Results

No values have been added to the multi-user custom field.

Notes

accountId is working for single user picker custom field type.

Workaround

Currently the name parameter is supported, this would be the username of the user you wish to add like below:

{
    "fields": {
        "customfield_10055": [
            {
                "name": "admin"
            }
        ]
    }
}