Create minimal app

CSR.Application/Interfaces/IUserService.cs

@@ -10,4 +10,8 @@ public interface IUserService
      string email,
      string password
      );
+
+  record LoginResult(Domain.Entities.User? User, string? Error);
+  
+  Task<LoginResult> Login(string username, string password);
 }

CSR.Application/Services/UserService.cs

@@ -50,4 +50,20 @@ public class UserService(IUserRepository userRepository, Domain.Interfaces.IPass
 
     return new IUserService.RegisterNewUserResult(user, null);
   }
+  
+  public async Task<IUserService.LoginResult> Login(string username, string password)
+  {
+    var user = await _userRepository.GetByUsernameAsync(username);
+    if (user == null)
+    {
+      return new IUserService.LoginResult(null, "User not found.");
+    }
+
+    if (!user.VerifyPassword(password, _passwordHasher))
+    {
+      return new IUserService.LoginResult(null, "Wrong password.");
+    }
+
+    return new IUserService.LoginResult(user, null);
+  }
 }