[Bug] Fix the undeclared variables in server.js

[gbowne1]

Fix the undeclared variables 'User' and 'bcryptSalt' in server.js

[gbowne1]

@jzunigarce fix the arrow function to => in errorHandlers.js

const withErrorStack = (message, err, stack) =≥ {
  if(env === 'development') {
    return {...err, message, stack};
  }
  return err;
}

[jzunigarce]

I made a PR, please update the main branch

[gbowne1]

Ok, thanks. Done.