feat StayExport - Initial Implementation

- Created models for DB and DTOs: StayExportFile
- Added required db migrations.
- Added StayExportService and StayExportServiceFactory for stay exporting services.
- Added configuration options required for StayExport.

src/Somnia.GuestLog/Models/Entities/GuestAddress.cs

@@ -1,3 +1,5 @@
+using Somnia.GuestLog.Infrastructure;
+
 namespace Somnia.GuestLog.Models.Entities;
 
 public class GuestAddress : BaseEntity
@@ -9,5 +11,5 @@ public class GuestAddress : BaseEntity
     public required string AddressCountry { get; set; }
     public string? ZipCode { get; set; }
 
-    public override string GetFullKey() => "N/A";
+    public override string GetFullKey() => DbConsts.PK_NotApply;
 }