Added max list size circumvention for file transfers between sites.

SharepointToolbox/Services/BulkSiteService.cs

@@ -54,6 +54,9 @@ public class BulkSiteService : IBulkSiteService
         var owners = ParseEmails(row.Owners);
         var members = ParseEmails(row.Members);
 
+        if (owners.Count == 0)
+            throw new InvalidOperationException($"Team site '{row.Name}' requires at least one owner.");
+
         var creationInfo = new TeamSiteCollectionCreationInformation
         {
             DisplayName = row.Name,
@@ -88,6 +91,7 @@ public class BulkSiteService : IBulkSiteService
                     membersGroup.Users.AddUser(user);
                     await ExecuteQueryRetryHelper.ExecuteQueryRetryAsync(siteCtx, progress, ct);
                 }
+                catch (OperationCanceledException) { throw; }
                 catch (Exception ex)
                 {
                     Log.Warning("Failed to add member {Email} to {Site}: {Error}",
@@ -142,6 +146,7 @@ public class BulkSiteService : IBulkSiteService
                 ownersGroup.Users.AddUser(user);
                 await ExecuteQueryRetryHelper.ExecuteQueryRetryAsync(siteCtx, progress, ct);
             }
+            catch (OperationCanceledException) { throw; }
             catch (Exception ex)
             {
                 Log.Warning("Failed to add owner {Email} to {Site}: {Error}",
@@ -162,6 +167,7 @@ public class BulkSiteService : IBulkSiteService
                 membersGroup.Users.AddUser(user);
                 await ExecuteQueryRetryHelper.ExecuteQueryRetryAsync(siteCtx, progress, ct);
             }
+            catch (OperationCanceledException) { throw; }
             catch (Exception ex)
             {
                 Log.Warning("Failed to add member {Email} to {Site}: {Error}",