Add integration test for built image

[greg-el]

Having integration tests for the built image would be very useful in catching any issues not covered by unit tests.

The 1.3.2 release bumped stream collector to 2.7.1. Stream collector 2.7.0 included an addition of a new required key for the collector config. As this was not updated in the Micro default collector config (src/main/resources/application.conf) the image failed to run, as the parsing of the now-invalid config failed. Although there is now a unit test for an invalid config, a full integration test would catch anything else lurking, not covered by unit tests, as mentioned by @istreeter here.

testcontainers is likely a good way to set integration tests up, which could include sending events to the built Micro image, and checking they exist in /good