Directory-level approval configuration

[marshall7m]

Allow users to define a config file such as approval_ci.yaml within each Terraform directory that contains directory-level approval configurations. This allows PR contributors to dynamically set these configurations within their PR rather than relying on the default configuration specified as input in this Terraform module.

The config file can look something like this:

include_parent: true
voters:
  John:
    email: [email protected]
    sms: 123-456-7890
    slack: john123
    notify_on:
    - failure
    - success
min_approval_count: 2
min_rejection_count: 2

include_parent: true will result in the first parent approval_ci.yaml configuration being merged with the child configuration (inspired by Terragrunt include block)