Config management pipeline

[Aenima4six2]

ArgoCD already supports defining custom config management tools, however, often times we just want to augment the input or output of an already supported tool (like Kustomize). What would be great, is if the ArgoCD Application spec supported a pre-exec and post-exec field. These fields would not alter the target config management tool, but would allow users to run a custom utility before and after the configured management tool executed. If using Kustomize, the result would yield something like <pre-exec-tool> | kustomize build ... | <post-exec-tool>