openeo grass driver: fix apply process

[metzm]

fix parsing of the process graph inside the apply process definition

[griembauer]

Thanks, I also added a basename parameter to t.rast.mapcalc, because it will fail without it. Local testing was successful with the operators in OPERATOR_DICT and FN_DICT. However, using apply with two different datasets seems not to be possible at the moment, as arguments["data"] is explicitly parsed in this PR and constructions like the following cannot be validated:

[...]
    "apply1": {
      "process_id": "apply",
      "arguments": {
        "data": {
          "from_node": "loadcollection1"
        },
        "process": {
          "process_graph": {
            "lte1": {
              "process_id": "subtract",
              "arguments": {
                "x": 1,
                "y": {
                  "from_argument": "data"
                }
              },
              "result": true
            }
          }
        }
      }
# how to pass two datasets as data arguments to the following node?
    },
    "apply2": {
      "process_id": "apply",
      "arguments": {
        "data1": {
          "from_node": "loadcollection1"
        },
        "data2": {
          "from_node": "apply1"
        },
        "process": {
          "process_graph": {
            "lte1": {
              "process_id": "divide",
              "arguments": {
                "x": {
                  "from_argument": "data1"
                },
                "y": {
                  "from_argument": "data2"
                }
              },
              "result": true
            }
          }
        }
      }
    },
[...]

Validation then yields:

{
  "id": "2021-07-28T11:45:12.380149",
  "code": "Bad Request",
  "message": "'NoneType' object has no attribute 'output_objects'",
  "links": []

However this may be subject to a dedicated PR.

[metzm]

apply (Apply a process to each pixel) is one of the officially defined openeo processes: https://processes.openeo.org/#apply and takes only one single datacube as input. Passing two datasets is not allowed because it would violate the API.

What you have in mind with several datasets as input would be in openeo an array of raster-cubes which is not defined in https://github.com/Open-EO/openeo-processes/blob/master/meta/subtype-schemas.json but we might need such arrays of raster-cubes as input for some of our backend-specific processes.

[mmacata]

Thanks! Please merge.