Admin controller, Locations controller, requests to add available countries, request to get available countries

SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/Exceptions/ApplicantNotFoundByUserIdException.cs

@@ -0,0 +1,10 @@
+using Domains.ApplicantDomain;
+using Infrastructure.Database.GeneralExceptions;
+
+namespace Infrastructure.Database.Applicants.Repositories.Exceptions
+{
+    public class ApplicantNotFoundByUserIdException(Guid id) : EntityNotFoundException<Applicant>("Applicant not found.")
+    {
+        public Guid UserId { get; private set; } = id;
+    }
+}