Update ESS-DIVE valid example for bertron metadata creation

[vchendrix]

Update the ESS-DIVE valid example in the documentation to demonstrate how metadata will be created for bertron datasets.

Details:

• If a dataset has no location, create an entity of type dataset with no coordinates.
• If a dataset has location information, create an entity of type site with:
  • description set as the geographic description
  • name set as the dataset name

Example transformation:

Original:

{
  "ber_data_source": "ESS-DIVE",
  "coordinates": {
    "latitude": 65.162309,
    "longitude": -164.819851,
    "altitude": null,
    "depth": null,
    "elevation": null
  },
  "entity_type": ["unspecified"],
  "description": "Maps of land surface phenology derived from PlanetScope data, 2018-2022, Teller, Kougarok, and Council, Seward Peninsula",
  "id": "doi:10.15485/2441497",
  "name": "NGEE Arctic Kougarok Site, Mile Marker 64, Alaska",
  "alt_ids": ["NGA547"],
  "alt_names": null,
  "part_of_collection": [],
  "uri": "https://data.ess-dive.lbl.gov/view/doi:10.15485/2441497"
}

Becomes:

{
  "ber_data_source": "ESS-DIVE",
  "coordinates": {
    "latitude": 65.162309,
    "longitude": -164.819851,
    "altitude": null,
    "depth": null,
    "elevation": null
  },
  "entity_type": ["site"],
  "name": "Maps of land surface phenology derived from PlanetScope data, 2018-2022, Teller, Kougarok, and Council, Seward Peninsula",
  "id": "doi:10.15485/2441497",
  "description": "NGEE Arctic Kougarok Site, Mile Marker 64, Alaska",
  "alt_ids": ["NGA547"],
  "part_of_collection": [],
  "uri": "https://data.ess-dive.lbl.gov/view/doi:10.15485/2441497"
}

Also, add an example of a dataset without locations, using entity type dataset and leaving coordinates blank or omitted.

[aclum]

i think the best practice is to leave off keys if the value is null instead of having the key...unless there is some value in storing that a value is null (this is sometimes true for example taxonomic information which is not resolvable down to a species level).