Migrate envoy tests to use a buildable test image

[tjons]

Currently, a number of our tests use the openpolicyagent/demo-test-server:v1 image, which I cannot seem to locate the source for and which does not support linux/arm64 architectures. To encourage well-tested contributions from a variety of users, I think we should either a) locate the source code for this image and link to it in the repo, as well as ensure that it is built for a variety of common OS+Arch's. Or, b) switch to something else which we can point users to source code for.

@anderseknert @srenatus @ashutosh-narkar open call: anyone able to share the source repo for openpolicyagent/demo-test-server? If so, are you open to me adding support for some different architectures?

[srenatus]

FWIW We had been building containers with yages at some point for EOPA's tests. Fortio also has a gRPC testserver, too, but I don't know if they build an image for it.

[srenatus]

Turns out I read too much into this -- openpolicyagent/demo-test-server isn't, and doesn't need to be, a gRPC service, right? I think anything there would do, even a simple python -m http.server serving nothing 😅

[anderseknert]

Let's get rid of that in tests then, and use something that makes it obvious what it is. nginx, maybe? I don't fully understand the purpose this has served, but based on what Stephan said, it sounds like that would work?

[ashutosh-narkar]

@tjons the code for openpolicyagent/demo-test-server:v1 is here. It's a simple Go HTTP server. We can add a link to the repo in the docs or if have something else in mind that's fine too.

[ashutosh-narkar]

I don't fully understand the purpose this has served,

@anderseknert it's a demo app that is used in this tutorial for showing an end-to-end example.

Currently, a number of our tests use the openpolicyagent/demo-test-server:v1 image

@tjons which tests are using this? I thought only the tutorials use this.