deploy portal service to GKE via GAE

[SKairinos]

Create a workflow in GitHub Actions that will auto-deploy the new service based on semantic releases.

See this tutorial

TODO:

• [ ] Only run pipeline if a new semantic version is being released.
• [ ] Create a Dockerfile that builds our service into an executable image.
• [ ] Push the Docker image to an image registry.
• [ ] Upsert the deployment on GKE. Ensure to configure the imagePullPolicy!
• [ ] Upsert the service on GKE.
• [ ] Parameterize pipeline so it can deploy to their respective environments.