docs: update endpoints to use file-routing approach (#5397)

- Move the original guides for creating endpoints and middlewares to sub-sections in the Endpoints category.
- Replace existing guides for endpoints and middlewares with the new approach.
- Update all endpoints-related snippets across docs to use this new approach.

www/apps/docs/content/admin/routes.md

@@ -356,9 +356,9 @@ const CustomPage = () => {
 export default CustomPage
 ```
 
-### Custom Endpoints
+### Custom API Routes
 
-You can also use `medusa-react` to interact with custom endpoints using [Custom Hooks utility functions](../medusa-react/overview.mdx#custom-hooks).
+You can also use `medusa-react` to interact with custom API Routes using [Custom Hooks utility functions](../medusa-react/overview.mdx#custom-hooks).
 
 ---
 

www/apps/docs/content/admin/setting-pages.md

@@ -337,9 +337,9 @@ export const config: SettingConfig = {
 export default CustomSettingPage
 ```
 
-### Custom Endpoints
+### Custom API Routes
 
-You can also use `medusa-react` to interact with custom endpoints using [Custom Hooks utility functions](../medusa-react/overview.mdx#custom-hooks).
+You can also use `medusa-react` to interact with custom API Routes using [Custom Hooks utility functions](../medusa-react/overview.mdx#custom-hooks).
 
 ---
 

www/apps/docs/content/admin/widgets.md

@@ -1270,9 +1270,9 @@ export const config: WidgetConfig = {
 export default ProductWidget
 ```
 
-### Custom Endpoints
+### Custom API Routes
 
-You can also use `medusa-react` to interact with custom endpoints using the [createCustomAdminHooks utility function](../medusa-react/overview.mdx#custom-hooks).
+You can also use `medusa-react` to interact with custom API Routes using the [createCustomAdminHooks utility function](../medusa-react/overview.mdx#custom-hooks).
 
 ---