Coredns integration with K8s-charm

[louiseschmidtgen]

Description

This PR adds the coredns integration to the k8s charm.

Handle Integration

• Checks for a new dns-provider relation between the k8s-charm and coredns.
• Disables built in dns if this relation exists
• Gets dns bits and configures coredns

Integration Tests

• add a coredns-model fixture, this juju model gets deployed on a new k8s cloud.
• The two tests checks for the cross-model-relation and the dns functionality.

limitation

The test_dns function can only be validated once cluster config bits are propagated properly.

[addyess]

Aight, here are some suggestions for the charm code. Looking at integration tests next

[addyess]

I've left some changes that will shrink this down a good bit. It's key to go learn about how pytest fixtures work. Not all my suggestions will be spot on -- but maybe they get close. Particularly on the model clean up

[addyess]

Looking pretty smooth. I had one little nit about using a command rather than a charm action

[addyess]

can we use the action on the charm now? Please check my logic -- this might yield a json kubeconfig file too...

Suggested change

	action = await k8s.run("k8s config")
	result = await action.wait()
	assert result.results["return-code"] == 0, "Failed to get kubeconfig with kubectl"
	kubeconfig_path = ops_test.tmp_path / "kubeconfig"
	kubeconfig_path.write_text(result.results["stdout"])
	action = await k8s.run_action("get-kubeconfig")
	result = await action.wait()
	assert result.results["return-code"] == 0, "Failed to get kubeconfig with kubectl"
	kubeconfig_path = ops_test.tmp_path / "kubeconfig"
	kubeconfig_path.write_text(result.results["kubeconfig"])

[louiseschmidtgen]

Doesn't seem to work just like that. I can take another look at this in the follow-up ticket. I'd like to get what we have merged for now.

[mateoflorido]

Some inquires

[addyess]

so, i wish this used the juju action instead of running through the snap CLI in order to make use of the public address of the unit

Suggested change

	action = await k8s.run("k8s config")
	result = await action.wait()
	assert result.results["return-code"] == 0, "Failed to get kubeconfig with kubectl"
	kubeconfig_path = ops_test.tmp_path / "kubeconfig"
	kubeconfig_path.write_text(result.results["stdout"])
	action = await k8s.run_action("get-kubeconfig")
	result = await action.wait()
	kubeconfig_path = ops_test.tmp_path / "kubeconfig"
	kubeconfig_path.write_text(result.results["kubeconfig"])

[addyess]

only request is that we use the charm action