Actions stored in private repositories within the organization can be reused across all repositories by referencing them in workflows. This ensures a centralized way of maintaining custom actions.
Encrypted secrets can be accessed across repositories in the same organization, making it easy to store sensitive data (like API keys or tokens) securely while allowing multiple workflows to access them.
Workflow templates allow you to create reusable templates for workflows that can be shared across repositories within the organization. This makes it easier to standardize processes and automate them across multiple projects.

Since the self-hosted runner is configured on a Linux VM and the script is written in PowerShell, you can invoke the script using the pwsh (PowerShell Core) shell in a run step in the workflow. This ensures that the script runs as-is on the Linux runner, as PowerShell Core (pwsh) is cross-platform and supports Linux.

The GITHUB_REF environment variable specifies the branch or tag that triggered the workflow. It contains the full reference to the branch or tag, such as refs/heads/main for a branch or refs/tags/v1.0 for a tag.

A: Use the actions/setup-docker action
B: Authenticate to the GitHub Container Registry.
C: Build the container image.
D: Push the image to the GitHub Container Registry
E: Pull the image from the GitHub Container Registry.

Some actions may require a GITHUB_TOKEN as an input to authenticate and perform specific tasks, such as creating issues, commenting on pull requests, or interacting with the GitHub API. In such cases, you would need to explicitly pass the token to the action.
When making an authenticated GitHub API request, the GITHUB_TOKEN is required to authenticate the request. This token is automatically provided by GitHub in the workflow, and it must be explicitly used when interacting with the GitHub API.