Big refactoring.

- clubs, booking platforms and user are now defined in customization files -> there are less environment variables
- the responsibility of the session moved
- booking cancellation is available

resa_padel/payload_builders.py

@@ -0,0 +1,12 @@
+from pathlib import Path
+
+from jinja2 import Environment, FileSystemLoader
+
+
+class PayloadBuilder:
+    @staticmethod
+    def build(template_path: Path, **kwargs) -> str:
+        environment = Environment(loader=FileSystemLoader(template_path.parent))
+        template = environment.get_template(template_path.name)
+
+        return template.render(**kwargs)