Remote build command using the Function Builder API

[alexellis]

This is a proposal for a remote build command using the Function Builder API, plus an SDK struct that can be vendored into a Go API / microservice to perform builds with the Function Builder API that OpenFaaS Pro offers.

https://docs.openfaas.com/openfaas-pro/builder/

Expected Behaviour

faas-cli publish --remote /faas-cli pro-build?

kubectl port-forward \
    -n openfaas \
    svc/pro-builder 8081:8080

kubectl get secret \
    -n openfaas payload-secret -o jsonpath='{.data.payload-secret}' \
    | base64 --decode \
    > builder-payload-secret.txt

faas-cli pro-build \
  -f stack.yml 
  --filter hello-world \
  --builder-url http://127.0.0.1:8081 \
  --build-token-file builder-payload-secret

Plus some kind of SDK:

imageRef, err:= sdk.RemoteBuild("./handler", "golang-middleware", "127.0.0.1:8081`, buildToken)

Current Behaviour

We have different code examples, but they're relatively complex and involve quite a few steps. Can we make it simpler to get started?

https://github.com/openfaas/function-builder-examples

Why do you need this?

I've seen interest in the Function Builder API from low-code companies or SaaS companies and want to make it more accessible for them to get started and try it out.