Creating a pipeline that automatically packages and deploys the application.
With the CI pipeline in place, we will now build the Continuous Delivery (CD) part. This pipeline will take the successfully tested code and prepare it for deployment. The first job in our CD pipeline will be to build a Docker image. Using the `Dockerfile` we created earlier, the pipeline will execute the `docker build` command. This will package our Node.js application, along with all its dependencies and the Node.js runtime itself, into a single, immutable artifact: a container image. This image will be tagged with a unique identifier, often the Git commit hash, to ensure traceability. Once the image is built, the next step is to push it to a container registry. A container registry, like Docker Hub, GitHub Container Registry, or Google Artifact Registry, is a storage system for your container images. The pipeline will authenticate with the registry and push the newly created image. Storing the image in a registry makes it available for deployment to any environment. Finally, the 'deploy' job will be configured. For this project, we can simulate a simple deployment by having the pipeline SSH into a server and run a `docker run` command to start a new container from the image we just pushed. In a more advanced setup, this step would use tools like Kubernetes or Terraform to manage the deployment. We will configure this deployment job to run only on pushes to the main branch, ensuring that only code that has been reviewed and merged gets deployed.