Feature.properties should be mandatory

[OlivierMartineau]

https://datatracker.ietf.org/doc/html/rfc7946#section-3.2

A Feature object has a member with the name "properties". The value of the properties member is an object (any JSON object or a JSON null value).

I found that you could remove a Feature "properties" property and still have the format validated.
Such property can be null or any object, possibly empty, but should always be there.

Delete line 609 to 611 in test/GeoJSON.integration.js: all tests are still successful.

[OlivierMartineau]

I suggest to change index.js line 496 to the following:

Feature.schemaName = 'Feature'

function validateFeature(feature) {
  if (!feature.type) {
    throw new mongoose.Error('Feature must have a type')
  }
  // type must be Feature
  if (feature.type !== 'Feature') {
    throw new mongoose.Error(feature.type + ' is not a valid GeoJSON type')
  }
  if (!feature.geometry) {
    throw new mongoose.Error('Feature must have a geometry')
  }
  // check for crs
  if (feature.crs) {
    crs = feature.crs
    validateCrs(crs)
  }
  validateGeometry(feature.geometry)
  validateFeatureProperties(feature.properties)
}

function validateFeatureProperties(properties) {
  if (properties === null) return
  if (!properties) {
    throw new mongoose.Error('Feature must have a "properties" member')
  }
  if (typeof properties !== 'object') {
    throw new mongoose.Error('Feature properties must be a JSON object or a null value.')
  }
}

[joshkopecek]

Hi @OlivierMartineau. Great suggestion. Feel free to make a PR for this.