Subswath not mandatory

[clausmichele]

Fixes #138

[clausmichele]

Test is failing, because the enum parameter for subswath in the CWL doesn't accept null as a valid input.

[EmileSonneveld]

@codex review

[EmileSonneveld]

@copilot review without making changes.

[clausmichele]

Tested with the following code and it worked. I'm pointing to a modified UDP, where the subswath is not required and using the CWL from this branch.

import openeo

connection = openeo.connect("openeo.dataspace.copernicus.eu/").authenticate_oidc()
stac_resource = connection.datacube_from_process(
    "sentinel1_sar_coherence",
    namespace="https://gist.githubusercontent.com/clausmichele/cec67bdc658487c544d380a0c0e924df/raw/a0eda5d74aa78cebb59a50df69560ad11cfe643d/sentinel1_sar_coherence.json",
    **{
        "spatial_extent": {
          "west": 10.930938606933454,
          "east": 11.09525568450856,
          "south": 46.740488579394516,
          "north": 46.82501382506073
        },
        "temporal_extent": ["2018-01-28", "2018-02-15"],
        "temporal_baseline": 6,
        "polarization": "VH",
        # "sub_swath": "IW2"
    }
)

job = stac_resource.create_job(title="sentinel1_sar_coherence aoi only")
job.start_and_wait()
job.get_results().download_files()

[EmileSonneveld]

@copilot review without making changes. (First review attempt got stuck)