TerraformEnvironmentStageShellHookPlugin: Support for one time run before running terraform commands

[codezninja]

I would like to run some custom bash scripts to setup my environment before running the terraform commands. Examples lets say I need aws-cli or python in my Docker container using AgentNodePlugin. Instead of my using a custom dockerfile. I would like to just run some custom shell comands before running init, plan & apply.

I dont' want to duplicate the same dockerfile over multiple projects and would like to utilize Customizations to setup the container with proper dependecies.