Add plan and approval stage for CodePipeline

[hoanglc]

Describe the outcome you'd like

When initializing the AFT product, I would love to have 2 another CodePipeline stages for each AFT repositories (account request, account customization, global customization and account provisioning customizations)
(1) Plan stage
Run "terraform plan"

(2) Approval stage
To avoid terraform code is applied without approval.

Is your feature request related to a problem you are currently experiencing? If so, please describe.

Customer want to have terraform plan output to detect any change if had. and also approval stage on CodePipeline to have double-check if something went wrong.

Additional context

CodePipeline with 2 stages. Wait for 2 additional stage

[rbhagyar]

Requesting this feature too. Right now looking at workarounds by modifying this through customizations.