feat: add ability to add ConfigMap checksum as resource annotations

[wyvernzora]

Note: draft change do not merge

One common practice that I have seen is adding the checksum of config map contents as annotations to workloads, so that when a config map is updated, the associated deployments can also get updated and bounced. This PR is an attempt to implement such functionality, though I am not sure about some aspects of this change and would appreciate some feedback.

Specific things that I'd like some feedback on:

• Should we expose the checksum as a property on ConfigMap? For example cm.checksum. While the type of that property would need to be string, but in fact it needs to be Lazy that produces a string. I am not sure what the practice is for exposing a Lazy as a property on a construct.
• Choosing to not expose the checksum outside the ConfigMap results in this awkward addChecksumTo() API. I'd appreciate any input on what would be a good API pattern for adding these checksum annotations.
• I had to add a dependency on json-stable-stringify to make sure that hashes come out consistent. What are the opinions of this project on adding dependencies?

[iliapolo]

node.id is unique only in a given scope, node.addr will give an app unique id.

Suggested change

	`checksum/${this.node.id}`,
	`cdk8s.io/config-map.${this.node.addr}.checksum`,

[iliapolo]

Please add documentation for this feature to https://github.com/cdk8s-team/cdk8s-plus/blob/k8s-30/main/docs/plus/config-map.md

[iliapolo]

@wyvernzora

Should we expose the checksum as a property on ConfigMap?

No need. At least not right now.

Choosing to not expose the checksum outside the ConfigMap results in this awkward addChecksumTo()

Agree. But its ok. Exposing lazy strings is also quite awkward.

I had to add a dependency on json-stable-stringify to make sure that hashes come out consistent. What are the opinions of this project on adding dependencies?

We try to avoid it, but also recognize sometimes it is needed. This seems like one of those times 👍

[github-actions]

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[burner1024]

Please reconsider.