Add note in tutorial for "x-kubernetes-preserve-unkown-fields"

[ztaylor54]

…." field, link to k8s docs on the topic

What do these changes do?

The result of discussion in #574

Adds a note in the walkthrough tutorial about CRDs requiring the x-kubernetes-preserve-unknown-fields: true field to be set in the CRD schema, as well as linking to relevant k8s docs on field pruning.

Description

The tutorial had not been updated to warn about Kubernetes silently pruning unknown fields, so this note should be helpful to anyone who brought their own CRD into the walkthrough and neglected to add the x-kubernetes-preserve-unknown-fields field to their schema, as I had.

Issues/PRs

Issues: #574

Related:

Type of changes

• Mostly documentation and examples (no code changes)

Checklist

• The code addresses only the mentioned problem, and this problem only
• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt

[nolar]

@ztaylor54 Thanks for the contribution!

[ztaylor54]

@nolar No problem, thanks for being so helpful last week!