Add public repository with Docker images for service callouts and plugins

[yanavlasov]

Please consider adding public Docker repository which is automatically updated with latest images of service extensions and plugins. This will simplify significantly demo setups and reference configuration.

[martijneken]

We have this. There's one for the plugins tester, and one for (some of the) callouts sample servers. They are published by a manually invoked GitHub "publish" actions on this project. The plugins tester is documented within this repo under plugins/, the callouts servers are referred to by some terraform samples and Google internal tests. What's the missing piece?

[martijneken]

What's the missing piece?

Answering my own question: we are not publishing any compiled plugins yet, and that is work in progress by @dallen68. Assigning this issue.

All samples are/will be available here:

• us-docker.pkg.dev/service-extensions-samples/callouts/...
• us-docker.pkg.dev/service-extensions-samples/plugins/...