Permission changes do not display vetos when canceled

Problem definition

When vetoing a permission change using one of the Global, Project or Repository *PermissionGrantRequestedEvent, *PermissionModificationRequestedEvent or *PermissionRevocationRequestedEvent types, the vetoes are not displayed in the UI. Instead, all the UI shows is "Permission grant canceled", "Permission modification canceled" or "Permission revocation canceled", respectively. That's not very helpful for users when it comes to understanding why they can't do something.

Steps to Reproduce

Install a custom app which listens for a cancelable permission event and cancels it.

Expected Results

The message provided when the event was canceled is displayed in the UI.

Actual Results

A canned message like "Permission grant canceled" is displayed, with no details about why the operation was canceled.

Notes

The server's REST response for the operation already includes the veto messages in a "details" list, but the UI does not display them.

Workaround

No workaround available.