Add note about Oracle and MySQL limitations for IncludeGraph feature

Author: fabien.menager

README.md

@@ -136,6 +136,8 @@ var blogs = new List<Blog>
 await dbContext.ExecuteBulkInsertAsync(blogs, o => o.IncludeGraph = true);
 ```
 
+> ℹ️ This feature is not available for Oracle and MySQL providers due to limitations in retrieving generated IDs.
+
 See [Graph Insert documentation](https://phenx.github.io/PhenX.EntityFrameworkCore.BulkInsert/graph-insert.html) for details.
 
 ### Conflict resolution / merge / upsert

docs/graph-insert.md

@@ -1,5 +1,7 @@
 # Graph Insert (Navigation Properties)
 
+> ℹ️ This feature is not available for Oracle and MySQL providers due to limitations in retrieving generated IDs.
+
 This library supports bulk inserting entire object graphs, including entities with their related navigation properties.
 
 ## Enabling Graph Insert