feat: support tag based policies

[codingdiaz]

Hey, I just made a Pull Request!

This should address #25232. It looks like the scaffolder action currently defaults to branch based protections. I added a new input to make this a non-breaking change. This could also be implemented by updating the structure of the parameter customBranchPolicyNames (and probably re-naming the input) to be an object. i.e. something like...

protections:
 - name: releases/*
   type: tag

https://docs.github.com/en/rest/deployments/branch-policies?apiVersion=2022-11-28#create-a-deployment-branch-policy

I tested this with a software template that looks like:

apiVersion: scaffolder.backstage.io/v1beta3
kind: Template
metadata:
  name: v1beta3-demo
  title: Test Action template
  description: scaffolder v1beta3 template demo
spec:
  owner: backstage/techdocs-core
  type: service

  parameters:
    - title: Fill in some steps
      required:
        - name
      properties:
        name:
          title: Name
          type: string
          description: Unique name not used

  # here's the steps that are executed in series in the scaffolder backend
  steps:
    - id: github-env
      name: GitHub Env
      action: github:environment:create
      input:
        repoUrl: github.com?repo=repo-name&owner=owner-name
        name: testing
        token: <redacted>
        deploymentBranchPolicy:
          custom_branch_policies: true
          protected_branches: false
        customTagPolicyNames:
          - releases/*

✔️ Checklist

• A changeset describing the change and affected packages. (more info)
• Added or updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)
• All your commits have a Signed-off-by line in the message. (more info)

[backstage-goalie]

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@backstage/plugin-scaffolder-backend-module-github	plugins/scaffolder-backend-module-github	minor	v0.3.0

[benjdlambert]

Nice thanks! 🙏 🎉

[github-actions]

Thank you for contributing to Backstage! The changes in this pull request will be part of the 1.29.0 release, scheduled for Tue, 16 Jul 2024.