First pass at semaphore

src/Core/Entities/DefaultCollectionSemaphore.cs

@@ -0,0 +1,8 @@
+namespace Bit.Core.Entities;
+
+public class DefaultCollectionSemaphore
+{
+    public Guid OrganizationId { get; set; }
+    public Guid OrganizationUserId { get; set; }
+    public DateTime CreationDate { get; set; } = DateTime.UtcNow;
+}

src/Core/Repositories/ICollectionRepository.cs

@@ -65,10 +65,21 @@ public interface ICollectionRepository : IRepository<Collection, Guid>
 
     /// <summary>
     /// Creates default user collections for the specified organization users if they do not already have one.
+    /// Uses the stored procedure approach with semaphore-based duplicate prevention.
     /// </summary>
     /// <param name="organizationId">The Organization ID.</param>
     /// <param name="organizationUserIds">The Organization User IDs to create default collections for.</param>
     /// <param name="defaultCollectionName">The encrypted string to use as the default collection name.</param>
     /// <returns></returns>
     Task UpsertDefaultCollectionsAsync(Guid organizationId, IEnumerable<Guid> organizationUserIds, string defaultCollectionName);
+
+    /// <summary>
+    /// Creates default user collections for the specified organization users using bulk insert operations.
+    /// Inserts semaphore entries before collections to prevent duplicates.
+    /// </summary>
+    /// <param name="organizationId">The Organization ID.</param>
+    /// <param name="organizationUserIds">The Organization User IDs to create default collections for.</param>
+    /// <param name="defaultCollectionName">The encrypted string to use as the default collection name.</param>
+    /// <returns></returns>
+    Task UpsertDefaultCollectionsBulkAsync(Guid organizationId, IEnumerable<Guid> organizationUserIds, string defaultCollectionName);
 }