The Users from custom fields control allows excluding selected users (sourced from a custom field) from the list of approvers resolved for a given group. It is available on both Group steps and Work Item Field Group steps.

Currently, this control only supports custom fields of type Single User Picker. This is limiting, as customers commonly use Multi-User Picker custom fields to represent reviewers, stakeholders, or excluded parties dynamically per work item.

We need to extend the control so that Multi-User Picker custom fields are also selectable. When such a field is selected, all users present in the field at the time of step evaluation should be excluded from the approver set resolved for the group.

Acceptance Criteria

• The Users from custom fields control lists both Single User Picker and Multi-User Picker custom fields as selectable options.

• The control behaves consistently on both Group steps and Work Item Field Group steps.

• When a Multi-User Picker field is selected, all users assigned to that field on the work item are excluded from the approver set resolved for the group at step evaluation time.

• Multiple custom fields (any mix of Single User Picker and Multi-User Picker) can be configured in the same control.

• Empty Multi-User Picker fields resolve to an empty exclusion set without breaking step evaluation.

• Configuration is persisted in the AP definition and survives import/export.

• Existing step definitions using Single User Picker fields remain backward compatible.