#31 API basic implementation Cleanup

* cleans code
* reworks many code fragments into smaller methods and split into super class

api/utils/serializer/serializer.py

@@ -117,4 +117,21 @@ class AbstractModelAPISerializer:
         if isinstance(geojson, dict):
             geojson = json.dumps(geojson)
         geometry = geos.fromstr(geojson)
-        return geometry
+        return geometry
+
+    def get_obj_from_db(self, id, user):
+        """ Returns the object from database
+
+        Fails if id not found or user does not have shared access
+
+        Args:
+            id (str): The object's id
+            user (User): The API user
+
+        Returns:
+
+        """
+        return self.model.objects.get(
+            id=id,
+            users__in=[user]
+        )