Add UTMCoordinate class

- the class is a utility to abstract working with latitude-longitude
  coordinates in their UTM representation (~ "cartesian plane")
- the class's .x and .y properties enable working with simple x-y
  coordinates where the (0, 0) origin is the lower-left of a city's
  viewport

src/urban_meal_delivery/db/utils/__init__.py

@@ -0,0 +1,3 @@
+"""Utilities used by the ORM models."""
+
+from urban_meal_delivery.db.utils.coordinates import UTMCoordinate  # noqa:F401