Integration tests to cover startup files

[juha-aiven]

What is currently missing?

Lately https://github.com/aiven/karapace/pull/210/files#diff-a79ae23c164ad9d4d7ba51504e6d20f25dbbdc2b59f4d91bc2f105e3da9a6e63R51 caused karapace_all to fail. This was later fixed by https://github.com/aiven/karapace/pull/240.

Currently integration test are run in the CI pipeline only against the internally started pytest fixture that starts up Karapace. This fails to capture issues in the startup files that are used when Karapace is deployed somewhere.

How could this be improved?

One approach would be that the integration tests would be run against Karapace started from the main files karapace_all (both schema registry and Kafka REST) and from karapace.kafka_rest_apis (Kafka REST) & karapace.schema_registry_apis (Schema Registry).