Added authentication and authorization, updated dependency injections, removed hard-coded connection string

SchengenVisaApi/ApplicationLayer/AuthServices/RegisterService/Exceptions/UserAlreadyExistsException.cs

@@ -0,0 +1,6 @@
+using ApplicationLayer.AuthServices.Requests;
+
+namespace ApplicationLayer.AuthServices.RegisterService.Exceptions
+{
+    public class UserAlreadyExistsException(RegisterApplicantRequest request) : Exception($"User with email '{request.Email}' already exists");
+}

SchengenVisaApi/ApplicationLayer/AuthServices/RegisterService/IRegisterService.cs

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+using ApplicationLayer.AuthServices.Requests;
+
+namespace ApplicationLayer.AuthServices.RegisterService
+{
+    /// Handles <see cref="RegisterApplicantRequest"/>
+    public interface IRegisterService
+    {
+        /// Handle <see cref="RegisterApplicantRequest"/>
+        Task Register(RegisterApplicantRequest request, CancellationToken cancellationToken);
+    }
+}

SchengenVisaApi/ApplicationLayer/AuthServices/RegisterService/RegisterService.cs

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+using ApplicationLayer.AuthServices.NeededServices;
+using ApplicationLayer.AuthServices.RegisterService.Exceptions;
+using ApplicationLayer.AuthServices.Requests;
+using Domains.Users;
+
+namespace ApplicationLayer.AuthServices.RegisterService
+{
+    /// <inheritdoc cref="IRegisterService"/>
+    public class RegisterService(IUsersRepository users) : IRegisterService
+    {
+        async Task IRegisterService.Register(RegisterApplicantRequest request, CancellationToken cancellationToken)
+        {
+            if (await users.FindByEmailAsync(request.Email, cancellationToken) is not null)
+            {
+                throw new UserAlreadyExistsException(request);
+            }
+
+            //TODO mapper
+            var user = new User
+            {
+                Email = request.Email,
+                Password = request.Password,
+                Role = Role.Applicant
+            };
+
+            await users.AddAsync(user, cancellationToken);
+            await users.SaveAsync(cancellationToken);
+            users.GetAllAsync(cancellationToken);
+        }
+    }
+}