docs: general improvements and additions (#12296)

www/apps/book/app/learn/fundamentals/data-models/manage-relationships/page.mdx

@@ -6,6 +6,12 @@ export const metadata = {
 
 In this chapter, you'll learn how to manage relationships between data models when creating, updating, or retrieving records using the module's main service.
 
+<Note>
+
+This chapter applies to data model relationships within the same module. To manage linked data models across modules, check out [Links](../../module-links/page.mdx) and [Query](../../module-links/query/page.mdx).
+
+</Note>
+
 ## Manage One-to-One Relationship
 
 ### BelongsTo Side of One-to-One