docs: additions and improvements to modules and DML documentation (#7854)

* docs: additions and improvements to modules and DML documentation

* small wording fix

www/apps/book/app/advanced-development/data-models/configure-properties/page.mdx

@@ -67,7 +67,7 @@ The `unique` method indicates that a property’s value must be unique in the da
 For example:
 
 export const uniqueHighlights = [
-  ["5", "unique", "Configure the `email` property to allow unique values only."]
+  ["4", "unique", "Configure the `email` property to allow unique values only."]
 ]
 
 ```ts highlights={uniqueHighlights}

www/apps/book/app/advanced-development/data-models/searchable-property/page.mdx

@@ -20,7 +20,11 @@ The `searchable` method of the `model` utility indicates that a `text` property
 
 For example:
 
-```ts
+export const searchableHighlights = [
+  ["4", "searchable", "Define the `name` property as searchable."]
+]
+
+```ts highlights={searchableHighlights}
 import { model } from "@medusajs/utils"
 
 const MyCustom = model.define("my_custom", {

www/apps/book/app/advanced-development/modules/container/page.mdx

@@ -14,8 +14,6 @@ So, resources in the module, such as services or loaders, can only resolve other
 
 - `logger`: A utility to log message in the Medusa application's logs.
 
-{/* TODO add other relevant resources, such as event bus */}
-
 ---
 
 ## Resolve Resources

www/apps/book/app/advanced-development/modules/isolation/page.mdx

@@ -0,0 +1,32 @@
+export const metadata = {
+  title: `${pageNumber} Module Isolation`,
+}
+
+# {metadata.title}
+
+In this chapter, you'll learn about how modules are isolated, and what that means for your custom development.
+
+<Note title="Summary">
+
+- Modules can't access resources, such as services, from other modules.
+- You can use Medusa's tools, explained in the next chapters, to extend modules or implement features across modules.
+
+</Note>
+
+## How are Modules Isolated?
+
+A module is unaware of any resources other than its own, such as services or data models. This means it can't access these resources if they're implemented in another module.
+
+For example, your custom module can't resolve the Product Module's main service or have direct relationships from its data model to another module's data model.
+
+---
+
+## Customize and Implement Features Across Modules
+
+In your Medusa application, you want to implement features that span across modules, or you want to extend existing modules to add new features.
+
+For example, you want to extend the Product Module to add new properties to the `Product` data model.
+
+Medusa provides the tools to implement these use cases while maintaining isolation between modules.
+
+The next chapters explain these tools and how to use them in your custom development.

www/apps/book/app/advanced-development/modules/remote-query/page.mdx

@@ -73,7 +73,7 @@ export async function GET(
 
   const query = remoteQueryObjectFromString({
     entryPoint: "my_custom",
-    fields: ["id", "test"],
+    fields: ["id", "name"],
   })
 
   res.json({

www/apps/book/app/advanced-development/modules/service-factory/page.mdx

@@ -172,3 +172,24 @@ For example, the following methods are generated for the code snippet above:
 Except for the `retrieve` method, the suffixed data model's name is plural.
 
 </Note>
+
+### Using a Constructor
+
+If you implement the `constructor` of your service, make sure to call `super` passing it `...arguments`.
+
+For example:
+
+```ts highlights={[["8"]]}
+import { MedusaService } from "@medusajs/utils"
+import MyCustom from "./models/my-custom"
+
+class HelloModuleService extends MedusaService({
+  MyCustom,
+}){
+  constructor() {
+    super(...arguments)
+  }
+}
+
+export default HelloModuleService
+```

www/apps/book/sidebar.mjs

@@ -107,8 +107,8 @@ export const sidebar = sidebarAttachHrefCommonOptions(
               title: "Service Factory",
             },
             {
-              path: "/advanced-development/modules/options",
-              title: "Module Options",
+              path: "/advanced-development/modules/isolation",
+              title: "Module Isolation",
             },
             {
               path: "/advanced-development/modules/remote-query",
@@ -122,6 +122,10 @@ export const sidebar = sidebarAttachHrefCommonOptions(
               path: "/advanced-development/modules/remote-link",
               title: "Remote Link",
             },
+            {
+              path: "/advanced-development/modules/options",
+              title: "Module Options",
+            },
           ],
         },
         {
@@ -143,10 +147,6 @@ export const sidebar = sidebarAttachHrefCommonOptions(
               path: "/advanced-development/data-models/relationships",
               title: "Relationships",
             },
-            {
-              path: "/advanced-development/data-models/relationship-cascades",
-              title: "Relationship Cascades",
-            },
             {
               path: "/advanced-development/data-models/indexes",
               title: "Data Model Index",