Configurations created from a CloudResource unable to find auth secrets

[chris-brindley]

Describe the bug
When attempting to provision a CloudResource using a Revision that has an auth secret in a different namespace, the Configuration triggers an event Authentication secret (spec.auth) does not exist and Terranetes does not attempt to run terraform plan.

To Reproduce
Steps to reproduce the behavior:

1. Create a git secret in the terraform-system namespace.

kubectl -n terraform-system create secret generic github-credentials \
    --from-literal=GIT_USERNAME=foo \
    --from-literal=GIT_PASSWORD=bar

2. Create a Revision that references this secret.

kubectl apply -f- <<EOT
apiVersion: terraform.appvia.io/v1alpha1
kind: Revision
metadata:
  name: bucket.v1
spec:
  plan:
    name: bucket
    categories: [gcp, bucket, gcs]
    description: Creates a GCS storage bucket
    revision: v1.0.0
  inputs:
    - key: name
      description: The name of the bucket you are provisioning
      required: true
  configuration:
    auth:
      name: github-credentials
      namespace: terraform-system
    module: "https://github.com/my-org/my-module-repo.git?ref=v1.0.0"
EOT

3. Attempt to deploy a CloudResource referencing this Revision.

kubectl apply -f- <<EOT
apiVersion: terraform.appvia.io/v1alpha1
kind: CloudResource
metadata:
  name: my-bucket
  namespace: tenant
spec:
  plan:
    name: bucket
    revision: v1.0.0
  providerRef:
    name: my-provider
  variables:
    name: my-test-bucket
EOT

4. Observe a failure in the Configuration resource indicating the auth secret does not exist.

kubectl -n tenant events
LAST SEEN             TYPE      REASON            OBJECT                          MESSAGE
4m5s (x13 over 64m)   Warning   Action Required   Configuration/my-bucket-xl9ck   Authentication secret (spec.auth) does not exist

Expected behavior
Terranetes should be able to provision the CloudResource correctly.

Screenshots
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Additional context
Add any other context about the problem here.

[chris-brindley]

I've proposed a fix for this and another similar issue with Plans not being found in #1689