Resolve competing cascade action: manually set FKID to null

util/Migrator/DbScripts/2025-12-20_02_OrganizationUser_MigrateDefaultCollection.sql

@@ -0,0 +1,26 @@
+-- Update OrganizationUser_MigrateDefaultCollection to set DefaultCollectionOwner = NULL
+-- when migrating default collections to shared collections during OrganizationUser deletion
+
+CREATE OR ALTER PROCEDURE [dbo].[OrganizationUser_MigrateDefaultCollection]
+    @Ids [dbo].[GuidIdArray] READONLY
+AS
+BEGIN
+    SET NOCOUNT ON
+    DECLARE @UtcNow DATETIME2(7) = GETUTCDATE();
+
+    UPDATE c
+    SET
+        [DefaultUserCollectionEmail] = CASE WHEN c.[DefaultUserCollectionEmail] IS NULL THEN u.[Email] ELSE c.[DefaultUserCollectionEmail] END,
+        [RevisionDate] = @UtcNow,
+        [Type] = 0,
+        [DefaultCollectionOwner] = NULL
+    FROM
+        [dbo].[Collection] c
+        INNER JOIN [dbo].[CollectionUser] cu ON c.[Id] = cu.[CollectionId]
+        INNER JOIN [dbo].[OrganizationUser] ou ON cu.[OrganizationUserId] = ou.[Id]
+        INNER JOIN [dbo].[User] u ON ou.[UserId] = u.[Id]
+        INNER JOIN @Ids i ON ou.[Id] = i.[Id]
+    WHERE
+        c.[Type] = 1
+END
+GO