kapp reports incorrect diff for a resource having no annotation and spec updated by a webhook

[prembhaskal]

What steps did you take:
[A clear and concise description steps and any files that can be used to reproduce the problem.]
I deployed a package install resource with below yaml

---
apiVersion: packaging.carvel.dev/v1alpha1
kind: PackageInstall
metadata:
  name: pkg-demo
spec:
  packageRef:
    refName: simple-app.corp.com
    versionSelection:
      constraints: 1.0.1
  values:
  - secretRef:
      name: pkg-demo-values

A webhook adds below fields in the resources

spec.defaultNamespace: some-namespace
spec.serviceAccountName: some-sa

What happened:

When I deploy the same file again, kapp reports the fields added by webhook in the diff

Target cluster 'https://pni-stable.stacks.bluesky.tmc-dev.cloud.vmware.com/org/7b5a3524-a142-468e-98e5-9044ec534643/project/997b9b08-6baa-4224-85ff-f36fb7da6660/clustergroup/test-run'

@@ update packageinstall/pkg-demo (packaging.carvel.dev/v1alpha1) namespace: default @@
  ...
  spec:
-   defaultNamespace: unusable-namespace
    packageRef:
      refName: simple-app.corp.com
  ...
        constraints: 1.0.1
-   serviceAccountName: pkg-installs-sa
    values:
    - secretRef:

Changes

Namespace  Name      Kind            Age  Op      Op st.  Wait to    Rs       Ri  
default    pkg-demo  PackageInstall  11s  update  -       reconcile  ongoing  Waiting for generation 1 to be  
                                                                              observed  

Op:      0 create, 0 delete, 1 update, 0 noop, 0 exists
Wait to: 1 reconcile, 0 delete, 0 noop

What did you expect:
kapp should not report any diff for fields added by a webhook since there is no change in the resource.

Anything else you would like to add:
[Additional information that will assist in solving the issue.]

Environment:

• kapp version (use kapp --version):
  kapp version 0.59.0

• OS (e.g. from /etc/os-release):
  mac os

• Kubernetes version (use kubectl version)

---

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