Cross namespace configmap mapping

[rahtr]

Is your feature request related to a problem?
Currently, to set up CARM, a ConfigMap must be created in the namespace where the controller is deployed. This approach works well in a single-tenancy model, but in a multi-tenancy model, it compromises modularity. For instance, if you have hundreds of teams, each with their own individual AWS account, you would end up managing a single ConfigMap in the controller's namespace. This not only complicates management but also increases the risk of errors. If an issue arises with the ConfigMap, all tenants are affected.

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
  name: ack-role-account-map
  namespace: $ACK_SYSTEM_NAMESPACE
data:
  "<TEAM_AWS_ACCOUNT_ID>": arn:aws:iam::<TEAM_AWS_ACCOUNT_ID>:role/<TEAM_AWS_ACCOUNT_ROLE_NAME>
EOFF

Describe the solution you'd like
I do understand that k8s doesn't support cross referencing natively and as the shared informers are scoped per namespace for the namespace scoped objects, hence it would be difficult to implement it. We may need to explore alternative approaches to achieve this. For example, ESO ((https://external-secrets.io/v0.4.1/provider-aws-secrets-manager/) follows a per resource implementation. We could potentially follow a similar approach and retrieve the role from the namespace objects themselves.

Describe alternatives you've considered
None