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/development/plugins/create.mdx

@@ -196,17 +196,11 @@ Make sure to delete these files if you're not using them in your plugin.
 
 ### Plugin Structure
 
-While developing your plugin, you can create your TypeScript or JavaScript files under the `src` directory. This includes creating services, endpoints, migrations, and other resources.
+While developing your plugin, you can create your TypeScript or JavaScript files under the `src` directory. This includes creating services, API Routes, migrations, and other resources.
 
 However, before you test the changes on a Medusa backend or publish your plugin, you must transpile your files and move them either to a `dist` directory or to the root of the plugin's directory.
 
-For example, if you have an endpoint in `src/api/index.js`, after running the `build` or `watch` commands [as defined earlier](#recommended-change-scripts), the file should be transpiled into `dist/api/index.js` in your plugin's root. You can alternative transpile them into the `api/index.js` in your plugin's root.
-
-:::note
-
-It was previously required to output your files into the root of the plugin's directory (for example, `api/index.js` instead of `dist/api/index.js`). As of v1.8, you can either have your files in the root of the directory or under the `dist` directory.
-
-:::
+For example, if you have an API Route in `src/api/store/custom/route.ts`, after running the `build` or `watch` commands [as defined earlier](#recommended-change-scripts), the file should be transpiled into `dist/api/store/custom/route.ts` in your plugin's root. You can alternative transpile them into the `api/store/custom/route.ts` in your plugin's root.
 
 ### Development Resources
 
@@ -233,11 +227,11 @@ This guide doesn't cover how to create different files and components. If you’
   },
   {
     type: 'link',
-    href: '/development/endpoints/create',
-    label: 'Create an Endpoint',
+    href: '/development/api-routes/create',
+    label: 'Create an API Route',
     customProps: {
       icon: Icons['academic-cap-solid'],
-      description: 'Learn how to create an endpoint.'
+      description: 'Learn how to create an API Route.'
     }
   },
   {
@@ -364,27 +358,6 @@ class MyService extends TransactionBaseService {
 }
 ```
 
-You can also access the options in your plugin's endpoints. The second parameter that the function declared in `src/api/index.ts` receives is an object including your plugin's configurations.
-
-For example:
-
-```js title=src/api/index.ts
-// in an endpoint in your plugin
-export default (rootDirectory, options) => {
-  // options contain the plugin options
-  const router = Router()
-
-  router.get("/hello-world", (req, res) => {
-    res.json({
-      message: 
-      `Welcome to ${options.name ? options.name : "Medusa"}!`,
-    })
-  })
-
-  return router
-}
-```
-
 :::tip
 
 Make sure to include in the README of your plugin the options that can be passed to a plugin.