Added S3 support and services

PostFundManagement.Domain/Abstractions/IS3Service.cs

@@ -0,0 +1,7 @@
+namespace PostFundManagement.Domain.Abstractions;
+
+public interface IS3Service
+{
+    Task<Result<string>> UploadFileAsync(string fileName, Stream fileStream, string contentType, CancellationToken cancellationToken = default);
+    Task<Result> DeleteFileAsync(string fileKey, CancellationToken cancellationToken = default);
+}