Create a "coordinates" field type for Sealious Collections.
It should accept values as either an array of numbers (first lat, then lon), or an object ({lat: number, lon: number}), or a string like "12.12421,65.21312". It should be stored in a normalized way using GeoJSON (https://www.mongodb.com/docs/manual/reference/geojson/)
Remember to write tests for the field!