Improve coordinate validation

[duncandewhurst]

Location.coordinates specifies the use of WGS84 (EPSG:4326) projection which specifies a range of [-90, 90] for latitudes and [-180, 180] for longitudes.

Thanks to @cengkuru for the suggestion

[duncandewhurst]

Some relevant links:

• [Schema] Spatial coordinates format GFDRR/rdl-standard#197 (comment) proposes an approach for validating nested coordinate arrays (e.g. for polygon geometries)
• https://json-schema.org/understanding-json-schema/reference/array#tupleValidation could be used to apply different constraints to latitudes and longitudes

[duncandewhurst]

CoST Thailand data contains point geometries with coordinates of incorrect type (should be array, rather than array of arrays):

      "geometry" : {
        "type" : "Point",
        "coordinates" : [ [ "5.7712780573108", "101.20494886386501" ] ]
      },