End-to-end tests

We need to create end-to-end tests that treat Conduit as a black box, trigger requests to the API and make sure they produce the expected result. For now they should cover at least the main paths (e.g. creating a pipeline, starting it, stopping it, deleting it). These tests should be easy to run locally without setting up a specific environment (ideally with one make target), additionally we should trigger the tests in the CI as regression tests before merging any PR.

Start by locating the API entry points and the existing Make and CI configuration. Cover the main paths named in the issue—creating, starting, stopping, and deleting a pipeline—with black-box requests and expected results. Done means the tests run locally through one make target and execute in CI before pull requests merge.

Written by the indexing model from the issue text.