Kustomization per app

[laszlocph]

We use a single kustomization for all applications in an environment.

We should move (or add a possibility) to have a kustomization per app.

This would not cause deployment pipeline congestions/blocking, and allow per app healthchecks and timeout values.

The task is to add a manifest field to configure per app healthcheck / timeout values

[laszlocph]

it needs handling in two places:

• gimlet gitops write
• and in GimletD

Both should check if $env/flux/ folder has an Kustomization resource for $app Create one if there is none

[laszlocph]

• We have a single Flux kustomization in the gitops repo per env.
• We have apps in the $env/$app folder structure
• The Flux Kustomization points to $env only
• So all apps are deployed on the same pipe

It is errorprone, and also doesn't allow per app healthchecks So #40 will just create a Kustomization for each $env/$app folder