[PM-1632] Redirect on SsoRequired - return SsoOrganizationIdentifier (#6597)

feat: add SSO request validation and organization identifier lookup

- Implement SsoRequestValidator to validate SSO requirements
- Add UserSsoOrganizationIdentifierQuery to fetch organization identifiers
- Create SsoOrganizationIdentifier custom response for SSO redirects
- Add feature flag (RedirectOnSsoRequired) for gradual rollout
- Register validators and queries in dependency injection
- Create RequestValidationConstants to reduce magic strings
- Add comprehensive test coverage for validation logic
- Update BaseRequestValidator to consume SsoRequestValidator

test/Identity.Test/IdentityServer/TwoFactorAuthenticationValidatorTests.cs

@@ -32,7 +32,7 @@ public class TwoFactorAuthenticationValidatorTests
     private readonly IOrganizationUserRepository _organizationUserRepository;
     private readonly IOrganizationRepository _organizationRepository;
     private readonly IDataProtectorTokenFactory<SsoEmail2faSessionTokenable> _ssoEmail2faSessionTokenable;
-    private readonly ITwoFactorIsEnabledQuery _twoFactorenabledQuery;
+    private readonly ITwoFactorIsEnabledQuery _twoFactorEnabledQuery;
     private readonly ICurrentContext _currentContext;
     private readonly TwoFactorAuthenticationValidator _sut;
 
@@ -45,7 +45,7 @@ public class TwoFactorAuthenticationValidatorTests
         _organizationUserRepository = Substitute.For<IOrganizationUserRepository>();
         _organizationRepository = Substitute.For<IOrganizationRepository>();
         _ssoEmail2faSessionTokenable = Substitute.For<IDataProtectorTokenFactory<SsoEmail2faSessionTokenable>>();
-        _twoFactorenabledQuery = Substitute.For<ITwoFactorIsEnabledQuery>();
+        _twoFactorEnabledQuery = Substitute.For<ITwoFactorIsEnabledQuery>();
         _currentContext = Substitute.For<ICurrentContext>();
 
         _sut = new TwoFactorAuthenticationValidator(
@@ -56,7 +56,7 @@ public class TwoFactorAuthenticationValidatorTests
                     _organizationUserRepository,
                     _organizationRepository,
                     _ssoEmail2faSessionTokenable,
-                    _twoFactorenabledQuery,
+                    _twoFactorEnabledQuery,
                     _currentContext);
     }