EDR Metadata can now be harmonized

[maartenplieger]

Closes #359

This allows to configure extra metadata for the parameters in the Edr collection response

    <OgcApiEdr>
        <EdrCollection name="harmonie">
            <EdrParameter
                name="air_temperature__at_2m"
                unit="°C"
                standard_name="air_temperature"
                observed_property_label="Air temperature"
                parameter_label="Air temperature, 2 metre" />
        </EdrCollection>
    </OgcApiEdr>

To test:

• Follow instructions as in doc/tutorials/Configure_EDR_service.md
• Start the server and visit http://localhost:8080/edr/collections

The parameter in the collection endpoint now lists:

"parameter_names": {
    "air_temperature__at_2m": {
      "type": "Parameter",
      "id": "air_temperature__at_2m",
      "label": "Air temperature, 2 metre",
      "description": "harmonie - air_temperature__at_2m (air_temperature__at_2m)",
      "unit": {
        "symbol": {
          "value": "°C",
          "type": "http://www.opengis.net/def/uom/UCUM"
        }
      },
      "observedProperty": {
        "id": "https://vocab.nerc.ac.uk/standard_name/air_temperature",
        "label": "Air temperature"
      }
    }
  }