swh-journal: Add tests to the journal publisher using kafka instance
Testing the publisher with a real kafka instance through the pytest-kafka dependency.
This also:
- documents with a script how and what to install in regards to the kafka needed
- extracts the configuration checks done on the publisher via the cli and push those checks in the publisher directly.
- those checks are now tested (they helped in the debugging process of those tests)
- update the readme
Related T1276 Depends on D1280 Depends on D1282
Test Plan
tox
Migrated from D1239 (view on Phabricator)