feat StayExport - Refactor Export Services.

- Created new service: IStayExportService" for common export operations.
- Updated older services to be "IStayExportFormatProvider". This services will only implement the export format.
- Renamed "IStayExportServiceFactory" to "IStayExportFormatProviderFactory" as this factory now is used to get the format providers for the given format.

src/Somnia.GuestLog/Services/StayExport/StayExportProviderSpainParteViajeros.cs

@@ -0,0 +1,20 @@
+using Somnia.GuestLog.Enums.Models;
+using Somnia.GuestLog.Models.DTOs;
+
+namespace Somnia.GuestLog.Services.StayExport;
+
+public class StayExportProviderSpainParteViajeros(
+
+) : IStayExportFormatProvider
+{
+    private const string fileExtension = "xml";
+
+    public StayExportFormat GetFormat() => StayExportFormat.SpainParteViajeros;
+    public string GetFilename(DateTime exportTime)
+        => $"{Enum.GetName(GetFormat())}_{exportTime.ToFileTimeUtc()}.{fileExtension}";
+
+    public Task<StayExportFileResult> ExportDataAsync(IEnumerable<StayEntryDTO> stayList, Stream dataStream)
+    {
+        throw new NotImplementedException();
+    }
+}