Improve error handling?

[joelvdavies]

We could have a base exception e.g.

class APIException:
    status_code: int
    user_message: str

Then existing custom exceptions can override these (along with the usual message specified in the constructor). Then a custom exception handler can be used to catch all such exceptions and log/return their status code and user message (without any IDs), effectively recreating sections like

inventory-management-system-api/inventory_management_system_api/routers/v1/catalogue_category.py

Lines 135 to 138 in 3a1d6cb

	except LeafCategoryError as exc:
	message = "Adding a catalogue category to a leaf parent catalogue category is not allowed"
	logger.exception(message)
	raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail=message) from exc

But just by relying on raise LeafCategoryError, in this case the whole try/catch could be removed.

[joelvdavies]

A similar method to what I suggested here is now used on https://github.com/ral-facilities/object-storage-api. See ral-facilities/object-storage-api#15.