Use Peribolos for declarative GitHub Organisation management

[achrinza]

Peribolos is a CI utility maintained by the people at k8s that enables declaratively defining the GitHub Organisations' settings through a YAML file.

Benefits of adopting the declarative approach:

1. Better visibility on changes made and the discussion surrounding it through Pull Requests
2. Reduce the permissions needed by the maintainers
3. Allows anyone to suggest amendments and audit the GitHub Organisation without needing administrative privileges
4. Enforce certain users to be admins
5. Allow management of multiple GitHub Organisations through a single pane of glass

An example of Peribolos implemented with GitHub Actions:

https://github.com/cloudfoundry/community/blob/main/.github/workflows/org-management.yml