Add support for auth with Upbound identity and refactor kube client builder as an importable package

[turkenh]

Description of your changes

This PR adding support for authenticating with Upbound identity using session/robot tokens:

apiVersion: kubernetes.crossplane.io/v1alpha1
kind: ProviderConfig
metadata:
  name: kubernetes-provider
spec:
  credentials:
    source: Secret
    secretRef:
      namespace: crossplane-system
      name: cluster-config
      key: kubeconfig
  identity:
    type: UpboundTokens
    source: Secret
    secretRef:
      name: upbound-credentials
      namespace: crossplane-system
      key: token

With the number of identity providers increasing, I took the liberty of refactoring the relevant code piece so that we can consume the same package from the provider-helm (and other similar providers) instead of duplicating the code. After this PR, I'll open a PR to consume the package github.com/crossplane-contrib/provider-kubernetes/pkg/kube/ from provider-helm. It may not be the perfect solution but I believe it is a step forward and we can easily move it to a shared place (e.g. crossplane-runtime) if we decide to do so.

I have:

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

How has this code been tested

Configure & Create:

export UPBOUND_ACCOUNT=<YOUR_ACCOUNT>
export UPBOUND_TOKEN=<YOUR_API_TOKEN> # Robot tokens will be supported soon
export CONTROLPLANE_CONFIG=/tmp/controlplane-kubeconfig
rm -f $CONTROLPLANE_CONFIG

up alpha web-login -a $UPBOUND_ACCOUNT
KUBECONFIG=$CONTROLPLANE_CONFIG up ctx $UPBOUND_ACCOUNT/upbound-gcp-us-west-1/default/hasan-test

kubectl -n crossplane-system create secret generic cluster-config --from-file=kubeconfig=$CONTROLPLANE_CONFIG
kubectl -n crossplane-system create secret generic upbound-credentials --from-literal=token=$UPBOUND_TOKEN

kubectl apply -f examples/provider/provider-config-with-secret-upbound-identity.yaml
kubectl apply -f examples/object/object.yaml

Observe:

❯ kubectl get object
NAME               KIND        PROVIDERCONFIG        SYNCED   READY   AGE
sample-namespace   Namespace   kubernetes-provider   True     True    4s

❯ KUBECONFIG=$CONTROLPLANE_CONFIG kubectl get ns
NAME                STATUS   AGE
crossplane-system   Active   32h
default             Active   32h
kube-node-lease     Active   32h
kube-public         Active   32h
kube-system         Active   32h
sample-namespace    Active   4m20s
upbound-system      Active   32h

[haarchri]

@turkenh thanks for the implementation - i tested the implementation over time i got the following issue:

  Warning  CannotObserveExternalResource  2m8s (x2110 over 34h)  managed/object.kubernetes.crossplane.io  cannot get object: failed to get API group resources: unable to retrieve the complete list of server APIs: spaces.upbound.io/v1beta1: Get "https://upbound-gcp-us-west-1.space.mxe.upbound.io/apis/spaces.upbound.io/v1beta1": cannot get upbound org scoped token: Post "https://auth.upbound.io/apis/tokenexchange.upbound.io/v1alpha1/orgscopedtokens": context canceled

[haarchri]

yes looks like after 60 minutes something happens:

Events:
  Type     Reason                         Age                   From                                     Message
  ----     ------                         ----                  ----                                     -------
  Warning  CannotObserveExternalResource  2m23s (x46 over 42m)  managed/object.kubernetes.crossplane.io  cannot get object: failed to get API group resources: unable to retrieve the complete list of server APIs: spaces.upbound.io/v1beta1: Get "https://upbound-gcp-us-west-1.space.mxe.upbound.io/apis/spaces.upbound.io/v1beta1": cannot get upbound org scoped token: Post "https://auth.upbound.io/apis/tokenexchange.upbound.io/v1alpha1/orgscopedtokens": context canceled

NAME                                            KIND           PROVIDERCONFIG                               SYNCED   READY   AGE
object.kubernetes.crossplane.io/ctp-dev-69wbr   Secret         default                                      False    True    61m
object.kubernetes.crossplane.io/ctp-dev-bwqbl   ControlPlane   5ab0024e-fbc3-4a42-a1a1-a1dd4875093d-space   False    True    61m
object.kubernetes.crossplane.io/ctp-dev-qcj2n   Secret         default                                      False    True    61m

[turkenh]

yes looks like after 60 minutes something happens

@haarchri it should be fixed now.

Also, please note the small change in the identity type to be consistent with others, UpboundToken -> UpboundTokens.

[haarchri]

its working now:

object.kubernetes.crossplane.io/ctp-prod-cdd6x       Secret         default                                      True     True    83m
object.kubernetes.crossplane.io/ctp-prod-lgbtg       Secret         default                                      True     True    83m
object.kubernetes.crossplane.io/ctp-prod-wfzd4       ControlPlane   24bf1d49-140c-41e2-819e-15e14acf2538-space   True     True    83m

thanks for the implementation