Add kustomize support

[askmeegs]

Add Kustomize base + overlay structure to replace the following --

• hack script that produces kubernetes-manifests --> release/kubernetes-manifests workflow (use kustomize to inject image tag + generate manifests)

This will enable teams that need to customize the manifests, allowing them to either contribute their own overlay upstream, or fork the repo + build an overlay there.

[bourgeoisor]

This is planned and in our roadmap for 2022.

[bourgeoisor]

This is still planned, but we are looking into Bank of Anthos first. Commenting to reset SLO.

[bourgeoisor]

@NimJay with https://github.com/GoogleCloudPlatform/microservices-demo/tree/main/kustomize having merged upstream, could you describe what is left to be done for this issue -- for example a list of pending action items?

[NimJay]

Thanks for bringing this up, Olivier.
I believe there are a few things we need to do:

1. Add automation inside of the existing release automation (/hack/make-release-artifacts.sh) to generate the /kustomize/base/ folder. More details can be found in this comment.
2. Go through the flavours inside docs/ and identify which flavours need to be ported to Kustomize. I believe it's just the following we still need to worry about:
   1. /docs/service-mesh.md
   2. /docs/network-policies/
   3. /docs/workload-identity.md (we'd just be replacing the sed command in step 3)
3. Create a Kustomize component (inside /kustomize/components/) for each flavour identified in step 2. I've started work on porting over the /docs/network-policies/ flavour in Port NetworkPolicy flavour to Kustomize #1081.

[mathieu-benoit]

Closing this one as Kustomize is now officially documented and supported here: https://github.com/GoogleCloudPlatform/microservices-demo/tree/main/kustomize.

Let's add more variations/overlays by directly opening associated and specific PRs.