Impersonation does not work when a rule updates the same work item

[aok-foss]

Steps to reproduce

Make a rule that triggers on a work item update and then updates the same work item. Enable impersonation for that rule.

.impersonate=onBehalfOfInitiator
self.Description = self.Title;

Expected behavior

The rule triggers impersonated.

Actual behavior

No impersonation.

This is because inside TfsAggregator the WorkItemStore tries to emit a JsonPatchOperation that will do the impersonation:

aggregator-cli/src/aggregator-ruleng/WorkItemStore.cs

Line 158 in dbdf4b5

workItem.ChangedBy = _triggerIdentity;

But inside WorkItemWrapper the change is ignored:

aggregator-cli/src/aggregator-ruleng/WorkItemWrapper.cs

Line 368 in dbdf4b5

if (_item.Fields[field]?.Equals(value) ?? false)

Environment

Aggregator 1.0.0 running in Azure Functions on Windows