Fix crash on json-ld generation regarding collection's CRS

[IvanSanchez]

Overview

Found during the OGC/OSGeo/ASF codesprint in Évora. Briefly discussed in person with @tomkralidis.

While generating a json-ld document in my test instance (running master as of 2024-02-28, f4c2ff9), there's an error like

  File "..../pygeoapi/linked_data.py", line 138 in jsonldify_collection
    hascrs84 = crs.endswith('CRS84')
               ^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'endswith'

During runtime, the collection dict received by jsonldify looks like:

{
        (snip)
  "extent": {
    "spatial": {
      "bbox": [343500.0, 4401700.0, 519700.0, 4572100.0],
      "grid": [
        { "cellsCount": 881, "resolution": 200.0 },
        { "cellsCount": 852, "resolution": 200.0 },
      ],
    },
    "temporal": { "interval": [[None, None]] },
  },
  "crs": ["http://www.opengis.net/def/crs/OGC/1.3/25830"],
};

So, by changing crs = spatial_extent.get('crs') into crs = collection.get('crs')[0] makes the problem go away.

Since I'm not a pygeoapi expert, I'm not 100% sure that the collection dict is supposed to look like this.

Related issue / discussion

Additional information

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[IvanSanchez]

Superseded by #1561