Add test for non-python task

[tcompa]

• Write a minimal bash script conforming to the the right interface (./script.sh -j /path/to/args.json -o /path/to/out.json)
• Construct the task object, and set the appropriate command.
• Run it through fractal-server, e.g. as in test_runner_backends.py

[jluethi]

This will be very nice. E.g. if we'd want to integrate with the Java-based OME-NGFF converter from Glencoe to allow parsing of OME-compatible files to OME-Zarr (they just recently released their converter. I haven't tested it yet, but it may be a nice way to get access to more OME-Zarr parsing for diverse microscopes, though certainly wouldn't handle ROIs yet and probably not save things as individual images per well): https://github.com/glencoesoftware/NGFF-Converter Also, it has a GPL 2.0 license, so we can't directly depend on it from our BSD3 license repo.

But in general, integration with such tools should become easier with the support for arbitrary executables.

[tcompa]

How to proceed in practice:

• Prepare a script that takes --json and --metadata-out string arguments (this could be 1. python+argparse, 2. bash, 3. whatever, and the arguments are just ignored)
• Install fractal-server 1.0.4a0 or higher (this is to use the new endpoint)
• In a new test, add a task through the endpoint (see test_full_workflow.py::test_full_workflow for examples of how to call endpoints in tests), setting all attributes by hand in a TaskCreate payload.
• Apply the workflow (as in test_full_workflow), make assertions about outcome.

NOTE: all of this should first be tested with the local backend only, not with slurm,docker,etc..

More in detail: do not use the collect_tasks fixture, and replace

        # Add a dummy task
        res = await client.post(
            f"{PREFIX}/workflow/{workflow_id}/add-task/",
            json=dict(task_id=collect_packages[0].id),
        )

with something like

        # Create a new task
        ....
        # Add a task
        res = await client.post(
            f"{PREFIX}/workflow/{workflow_id}/add-task/",
            json=dict(task_id=new_task.id),
        )