[PM-28260] Optimize bulk reinvite endpoint (#6670)

* Implement optimized bulk invite resend command

- Added IBulkResendOrganizationInvitesCommand interface to define the bulk resend operation.
- Created BulkResendOrganizationInvitesCommand class to handle the logic for resending invites to multiple organization users.
- Integrated logging and validation to ensure only valid users receive invites.
- Included error handling for non-existent organizations and invalid user statuses.

* Add unit tests for BulkResendOrganizationInvitesCommand

- Implemented comprehensive test cases for the BulkResendOrganizationInvitesCommand class.
- Validated user statuses and ensured correct handling of valid and invalid users during bulk invite resends.
- Included tests for scenarios such as organization not found and empty user lists.
- Utilized Xunit and NSubstitute for effective testing and mocking of dependencies.

* Add IBulkResendOrganizationInvitesCommand to service collection

- Registered IBulkResendOrganizationInvitesCommand in the service collection for dependency injection.

* Update OrganizationUsersController to utilize IBulkResendOrganizationInvitesCommand

- Added IBulkResendOrganizationInvitesCommand to the OrganizationUsersController for handling bulk invite resends based on feature flag.
- Updated BulkReinvite method to conditionally use the new command or the legacy service based on the feature flag status.
- Enhanced unit tests to verify correct command usage depending on feature flag state, ensuring robust testing for both scenarios.

test/Api.Test/AdminConsole/Controllers/OrganizationUsersControllerTests.cs

@@ -11,6 +11,7 @@ using Bit.Core.AdminConsole.Models.Data.Organizations.Policies;
 using Bit.Core.AdminConsole.OrganizationFeatures.AccountRecovery;
 using Bit.Core.AdminConsole.OrganizationFeatures.OrganizationUsers.AutoConfirmUser;
 using Bit.Core.AdminConsole.OrganizationFeatures.OrganizationUsers.Interfaces;
+using Bit.Core.AdminConsole.OrganizationFeatures.OrganizationUsers.InviteUsers;
 using Bit.Core.AdminConsole.OrganizationFeatures.Policies;
 using Bit.Core.AdminConsole.OrganizationFeatures.Policies.PolicyRequirements;
 using Bit.Core.AdminConsole.Repositories;
@@ -730,4 +731,68 @@ public class OrganizationUsersControllerTests
         var problemResult = Assert.IsType<JsonHttpResult<ErrorResponseModel>>(result);
         Assert.Equal(StatusCodes.Status500InternalServerError, problemResult.StatusCode);
     }
+
+    [Theory]
+    [BitAutoData]
+    public async Task BulkReinvite_WhenFeatureFlagEnabled_UsesBulkResendOrganizationInvitesCommand(
+        Guid organizationId,
+        OrganizationUserBulkRequestModel bulkRequestModel,
+        List<OrganizationUser> organizationUsers,
+        Guid userId,
+        SutProvider<OrganizationUsersController> sutProvider)
+    {
+        // Arrange
+        sutProvider.GetDependency<ICurrentContext>().ManageUsers(organizationId).Returns(true);
+        sutProvider.GetDependency<IUserService>().GetProperUserId(Arg.Any<ClaimsPrincipal>()).Returns(userId);
+        sutProvider.GetDependency<IFeatureService>()
+            .IsEnabled(FeatureFlagKeys.IncreaseBulkReinviteLimitForCloud)
+            .Returns(true);
+
+        var expectedResults = organizationUsers.Select(u => Tuple.Create(u, "")).ToList();
+        sutProvider.GetDependency<IBulkResendOrganizationInvitesCommand>()
+            .BulkResendInvitesAsync(organizationId, userId, bulkRequestModel.Ids)
+            .Returns(expectedResults);
+
+        // Act
+        var response = await sutProvider.Sut.BulkReinvite(organizationId, bulkRequestModel);
+
+        // Assert
+        Assert.Equal(organizationUsers.Count, response.Data.Count());
+
+        await sutProvider.GetDependency<IBulkResendOrganizationInvitesCommand>()
+            .Received(1)
+            .BulkResendInvitesAsync(organizationId, userId, bulkRequestModel.Ids);
+    }
+
+    [Theory]
+    [BitAutoData]
+    public async Task BulkReinvite_WhenFeatureFlagDisabled_UsesLegacyOrganizationService(
+        Guid organizationId,
+        OrganizationUserBulkRequestModel bulkRequestModel,
+        List<OrganizationUser> organizationUsers,
+        Guid userId,
+        SutProvider<OrganizationUsersController> sutProvider)
+    {
+        // Arrange
+        sutProvider.GetDependency<ICurrentContext>().ManageUsers(organizationId).Returns(true);
+        sutProvider.GetDependency<IUserService>().GetProperUserId(Arg.Any<ClaimsPrincipal>()).Returns(userId);
+        sutProvider.GetDependency<IFeatureService>()
+            .IsEnabled(FeatureFlagKeys.IncreaseBulkReinviteLimitForCloud)
+            .Returns(false);
+
+        var expectedResults = organizationUsers.Select(u => Tuple.Create(u, "")).ToList();
+        sutProvider.GetDependency<IOrganizationService>()
+            .ResendInvitesAsync(organizationId, userId, bulkRequestModel.Ids)
+            .Returns(expectedResults);
+
+        // Act
+        var response = await sutProvider.Sut.BulkReinvite(organizationId, bulkRequestModel);
+
+        // Assert
+        Assert.Equal(organizationUsers.Count, response.Data.Count());
+
+        await sutProvider.GetDependency<IOrganizationService>()
+            .Received(1)
+            .ResendInvitesAsync(organizationId, userId, bulkRequestModel.Ids);
+    }
 }