if ( !completion )
    {
        return;
    }

    LETNetworkServiceSuccessBlock success = ^(NSURLSessionDataTask *task, id responseObject)
    {
        LETUser *user = [self.mappingService convertJSONDictionary:responseObject
                                                 toObjectWithClass:[LETUser class]
                                                     objectMapping:[LETUser userMappingJSONToObjectMapping]
                                                             error:nil];
        completion(user, nil);
    };

    LETNetworkServiceFailureBlock failure = ^(NSURLSessionDataTask *task, NSError *error)
    {
        [self.credentialsStorageService deleteLogin];
        [self.credentialsStorageService deletePassword];

        completion(nil, error);
    };

    [self.credentialsStorageService saveLogin:authInfo.email];
    [self.credentialsStorageService savePassword:authInfo.password];

    [self.networkService POST:kLETSignInApiMethod
                   parameters:nil
                      success:success
                      failure:failure];