refactor: refactor account related parts · Star-Academy/Summer1403-Project-Group01-Backend@c109f86

The following actions use a deprecated Node.js version and will be forced to run on node20: actions/checkout@v3, actions/setup-dotnet@v3. For more info: https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/

Non-nullable property 'SourceAccount' must contain a non-null value when exiting constructor. Consider declaring the property as nullable.

Non-nullable property 'DestinationAccount' must contain a non-null value when exiting constructor. Consider declaring the property as nullable.

The using directive for 'Application.DTOs.TransactionCsv' appeared previously in this namespace

'Result<T>.Fail(string)' hides inherited member 'Result.Fail(string)'. Use the new keyword if hiding was intended.