feat(loadgenerator): allow customizing frontend protocol

[aslafy-z]

Background

I would like to point locust to my nginx ingress instead of the service.

Change Summary

This PR adds support for customizing the protocol locust uses while querying the online-boutique website.

Additional Notes

Backwards compatible.

Testing Procedure

• Deploy the app with:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namespace: online-boutique
resources:
- https://github.com/GoogleCloudPlatform/microservices-demo//kustomize/base?ref=6af73dcf7fe1ca653d95ae7a29e12faf8cf02964
- ingress.yaml
components:
- https://github.com/GoogleCloudPlatform/microservices-demo//kustomize/components/network-policies?ref=6af73dcf7fe1ca653d95ae7a29e12faf8cf02964
- https://github.com/GoogleCloudPlatform/microservices-demo//kustomize/components/non-public-frontend?ref=6af73dcf7fe1ca653d95ae7a29e12faf8cf02964
patches:
- patch: |
  apiVersion: apps/v1
  kind: Deployment
  metadata:
    name: loadgenerator
  spec:
    template:
      spec:
        containers:
        - name: main
          image: ghcr.io/aslafy-z/microservices-demo/loadgenerator:483c6f731bb7c408ff5be379683b0ace8ea5833c
          env:
          - name: FRONTEND_PROTO
            value: https
          - name: FRONTEND_ADDR
            value: shop.example.com

• Ensure the load testing is running correctly looking at the logs