A GeoJSON object with the type "Feature" is a feature object:
A feature object must have a member with the name "geometry". The
value of the geometry member is a geometry object as defined above or a
JSON null value.
A feature object must have a member with the name "properties". The
value of the properties member is an object (any JSON object or a JSON null
value).
If a feature has a commonly used identifier, that identifier should
be included as a member of the feature object with the name "id".