Log outage geometries to database (#68)

To enable us to detect changes to to the geometry for future updating of the map (#67)

Reviewed-on: #68

geospatial.py

@@ -1,4 +1,5 @@
-from shapely import MultiPolygon, Polygon
+from shapely import MultiPolygon, Polygon, Geometry, to_wkb, from_wkb
+from sqlalchemy.types import TypeDecorator, LargeBinary
 
 
 def convert_outage_geometry(event) -> MultiPolygon:
@@ -9,3 +10,21 @@ def convert_outage_geometry(event) -> MultiPolygon:
     for ring in event["polygons"]["rings"]:
         polygon_list.append(Polygon(ring))
     return MultiPolygon(polygon_list)
+
+
+class DBGeometry(TypeDecorator):
+    impl = LargeBinary
+    cache_ok = True
+
+    def process_bind_param(self, value, dialect):
+        if isinstance(value, Geometry):
+            value = to_wkb(value)
+        return value
+
+    def process_result_value(self, value, dialect):
+        if value is None:
+            return value
+        else:
+            if not isinstance(value, Geometry):
+                value = from_wkb(value)
+            return value