ocrd_network base integration tests

[MehmedGIT]

This PR is just a basic beginning for the ocrd_network integration tests.

What does this PR include:

• Some extensions to MongoDB methods in ocrd_network for easier testing of the DB functionalities
• New state UNSET for jobs for easier testing instead of relying on None
• New endpoints to the Processing Server:
  • endpoint / for just testing the connectivity to the Processing Server
  • endpoint /workflow/job-simple/{workflow_job_id} - simplified endpoint for checking the overall status of a workflow
• Processing Server adds ocrd-dummy processor and queue by default when started:
  • This is a hack since there is no endpoint for worker registration yet
  • This will be refactored in the next PR when refactoring the ocrd_network and adding a dedicated endpoint
• A conftest.py provided for using fixtures for the MongoDB and RabbitMQ
• MongoDB integration tests
• RabbitMQ integration tests
• A dummy workflow consisting of 3 ocrd-dummy processors
• Basic Processing Server integration tests:
  • processing endpoint test with ocrd-dummy (1 processing worker deployed)
  • workflow endpoint execution and status check test with the dummy workflow
• Separate ocrd_logging.conf for the ocrd_network integration tests for easier catching of bugs when tests are failing
• Fixing .dockerignore to include relevant parts for the tests
• Extension to core Dockerfile for creating an ocrd_core_test image to be used by the testing containers
• Extension to core Makefile to allow make integration-test call
• Integration test workflow for Github Actions.

[kba]

Excellent, great work. a few minor questions, but ready for merge AFAICS. I'm running the tests and making sure that the multi-stage setup does not interfere with our other Docker deployments.

macos: I'll try to get it to work but it's not a blocker.

[kba]

Nice, that is a useful pattern we should apply widely.

[MehmedGIT]

If that works, I prefer using that instead of sleeping here and there to wait. So far I have not seen issues with that health check here and in Operandi.

[joschrew]

This are my first comments after I read through the changed source-code. I still have to find out why the tests fail on my side and then I will comment again.

[MehmedGIT]

Good to be shipped.