Refactor Kustomize components (service-accounts, shopping-assistant)

[bourgeoisor]

This PR:

• Embeds the service-accounts components directly in the services' respective manifest files
• Removes the disable-shopping-assistant component
• To replace it with a shopping-assistant component
• Toggles the default frontend "enable assistant" env from true to false

Note that this means the shopping assistant is no longer with the other services, but rather as part of a separate component.

Fixes #2468

Testing

I tested this by deploying with the following two components uncommented:

- ../kustomize/components/alloydb
- ../kustomize/components/shopping-assistant

Which deployed successfully with a working shopping assistant. And then I deployed with the two components commented out (the default state) which successfully deployed without the shopping assistant, as intended:

~ k get pods
NAME                                     READY   STATUS    RESTARTS   AGE
adservice-576758649-z4q4p                1/1     Running   0          2m13s
cartservice-6df4d5975f-7jhns             1/1     Running   0          2m13s
checkoutservice-985cc4c8-spcdk           1/1     Running   0          2m13s
currencyservice-cbc8b6f68-h9ltr          1/1     Running   0          2m13s
emailservice-6899dc7cb7-ddw6z            1/1     Running   0          2m13s
frontend-79fdcd47dc-rcdvp                1/1     Running   0          2m12s
loadgenerator-6b98d85996-t6ffx           1/1     Running   0          85s
paymentservice-59f4f479fc-gn9zk          1/1     Running   0          2m12s
productcatalogservice-55f98f957f-6nb2l   1/1     Running   0          2m12s
recommendationservice-6bb4576fd4-mdtxs   1/1     Running   0          2m11s
redis-cart-868cd7dff-pr4xs               1/1     Running   0          2m11s
shippingservice-8645b4d89d-nw95n         1/1     Running   0          2m11s

[github-actions]

🚲 PR staged at http://104.154.159.254

[github-actions]

🚲 PR staged at http://104.154.159.254

[moficodes]

It looks good but I think we can improve the sed experience with a kustomize overflow.

[moficodes]

Instead all these seds should we just add a overlay for these values?

[bourgeoisor]

The vars are in overlays already. Sed is just doing the var substitution with values.

If we have another overlays explicitly just for variables, then we still have to sed that overlay so we're back at square one. We can't hardcode those values in the overlay because they're dynamic, like the name of the GSA or the Google Cloud project ID.

Either way I spin it in my head, we need to either:
a) sed something; or
b) ask the user to manually replace vars somewhere (which is more friction than sed)

Unless I'm misunderstanding what you mean?

[moficodes]

/lgtm