Implement worker

Closes #2 (closed)

worker_generic_training_dataset/utils.py

+# -*- coding: utf-8 -*-
+import json
+import logging
+from logging import Logger
+from urllib.parse import urljoin
+
+from arkindex_worker.image import BoundingBox, polygon_bounding_box
+
+logger: Logger = logging.getLogger(__name__)
+
+
+def build_image_url(element) -> str:
+    bbox: BoundingBox = polygon_bounding_box(json.loads(element.polygon))
+    x: int
+    y: int
+    width: int
+    height: int
+    x, y, width, height = bbox
+    return urljoin(
+        element.image.url + "/", f"{x},{y},{width},{height}/full/0/default.jpg"
+    )