feat(hotelGroups): add offer display fields and related logic

- Add new database columns (coverImage, priceAmount, priceUnit, tags, status) to HotelGroup model
- Create hotel_group_dict serializer to handle image/coverImage synchronization and tag formatting
- Update site config endpoints to use the new serializer and filter published hotel groups
- Add Alembic migration for the new database schema changes
- Update test fixtures and API contract tests for the new fields
- Revise public and admin API documentation to document the new hotel group fields and usage rules

app/serializers.py

@@ -70,6 +70,16 @@ def product_dict(product) -> dict:
     return admin_product_dict(product)
 
 
+def hotel_group_dict(group) -> dict:
+    data = model_dict(group)
+    if not data.get("coverImage"):
+        data["coverImage"] = data.get("image")
+    if not data.get("image"):
+        data["image"] = data.get("coverImage")
+    data["tags"] = list(group.tags or [])
+    return data
+
+
 def destination_dict(destination, include_count: bool = False, product_count: int | None = None) -> dict:
     data = model_dict(destination, {"aliases": [model_dict(alias) for alias in _sorted_aliases(destination)]})
     if include_count: