Clarify how containers are tested an how to access the ones produced by the build (#4487)

Author: andreasohlund

README.md

@@ -16,6 +16,10 @@ A video demo showing how to set it up is available on the Particular YouTube cha
 
 [![](https://img.youtube.com/vi/w3tYnj11dQ8/0.jpg)](https://www.youtube.com/watch?v=w3tYnj11dQ8)
 
+### Containers
+
+All containers are [created on each build and pushed](.github/workflows/push-container-images.yml) to the [GitHub container registry](https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry) where the various instance type can be [accessed by their names](/.github/workflows/push-container-images.yml#L33) and run locally.
+
 ### Infrastructure setup
 
 If the instance is executed for the first time, it must set up the required infrastructure. To do so, once the instance is configured to use the selected transport and persister, run it in setup mode. This can be done by using the `Setup {instance name}` launch profile that is defined in 

docs/testing.md

@@ -35,3 +35,7 @@ Run ServiceControl full version and use the HTTP API to validate results. Learni
 ## Multi-instance tests
 
 Multi-instance tests validate the interaction between different ServiceControl instances. ServiceControl instances are run in-memory in the same process. LearningTransport is used for all tests.
+
+## Container tests
+
+Containers images generated for all builds are pushed to the [GitHub container registry](https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry). Once pushed all images are tested by [spinning them all up for each supported transport](/src/container-integration-test/).