Add exception handling if a horcrux is not found on the user's file storage service

[amansharma2910]

Right now, there is no error handling implemented for the case when due to some reason, a horcrux is not found on one of user's file storage services (for example in case the user deletes a horcrux by mistake).

Implement the error handling for uploads, downloads and delete API. In case the exception handling is triggered, delete the file record from the database as well, and then return a valid response in the form of {"message": "Horcrux not found on user's account. The file is no longer readable. Deleting from the chamber."}