Allow Object to define a set of connectionDetails

[st3v]

Description of your changes

This PR introduces a new property under Object.spec, named connectionDetails. This new property is optional and can be used to specify individual entries for a connection secret for the given resource. This essentially mirrors what we already have for provider-helm (i.e. Release.spec.connectionDetails). As such, the changes in this PR borrow heavily from crossplane-contrib/provider-helm#73.

The main difference between the implementation in provider-helm and this, is that here we do not require the resources referred to under connectionDetails to have a certain set of annotations or labels. While Helm makes sure that all resources belonging to a given release have a common set of annotations, we cannot assume the same here. This is because we're dealing with all sorts of external resources here managed by arbitrary controllers that do not share a common practice when it comes to putting a well-known set of annotations or labels on the child resources they control.

This PR consists of two commits. The first one adds the new property and reconciliation logic, as well as a set of corresponding test cases and additions to the composition example. The second commit updates pre-existing parts of the example to make use of the recently introduced Release.spec.connectionDetails[*].skipPartOfReleaseCheck in provider-helm. This one is really just housekeeping and somewhat orthogonal to the main purpose of this PR. I'd be happy to remove it from here and submit it in a separate PR if you think that would be better. Just let me know.

Fixes #15

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

• added new unit tests
• ran make test
• built the provider and installed it on my local cluster
• successfully verified a number of manual e2e scenarios in my local cluster

[st3v]

fyi @turkenh

[turkenh]

Thank you for your contribution @st3v 👍

Please also consider adding an example, or updating an existing one similar to here. This would make the feature more discoverable.

[turkenh]

Thanks for taking care of this 🙌

[st3v]

@turkenh You mean adding another example in addition to the arguably contrived one in my original commit?

provider-kubernetes/examples/in-composition/composition.yaml

Lines 217 to 229 in bfaf150

	connectionDetails:
	- apiVersion: v1
	kind: Service
	name: guestbook-ui
	namespace: argocd
	fieldPath: spec.clusterIP
	toConnectionSecretKey: host
	- apiVersion: v1
	kind: Service
	name: guestbook-ui
	namespace: argocd
	fieldPath: spec.ports[0].port
	toConnectionSecretKey: port

[turkenh]

@turkenh You mean adding another example in addition to the arguably contrived one in my original commit?

Yeah, to make it more discoverable, we can create a directory under example/object named connection-details for example and put an example there.

[schlakob]

Great feature! Looking forward using it! Are there any plans when this will be released?

[turkenh]

@schlakob just released https://github.com/crossplane-contrib/provider-kubernetes/releases/tag/v0.8.0 🚀