docs: add community maintained nestjs library (#3391)

docs/components/sidebar-content.tsx

@@ -1125,6 +1125,11 @@ C0.7,239.6,62.1,0.5,62.2,0.4c0,0,54,13.8,119.9,30.8S302.1,62,302.2,62c0.2,0,0.2,
 				icon: Icons.nitro,
 				href: "/docs/integrations/nitro",
 			},
+			{
+				title: "NestJS",
+				icon: Icons.nestJS,
+				href: "/docs/integrations/nestjs",
+			},
 			{
 				group: true,
 				title: "Mobile & Desktop",

docs/content/docs/integrations/nestjs.mdx

@@ -0,0 +1,82 @@
+---
+title: NestJS Integration
+description: Integrate Better Auth with NestJS.
+---
+
+This guide will show you how to integrate Better Auth with [NestJS](https://nestjs.com/).
+
+Before you start, make sure you have a Better Auth instance configured. If you haven't done that yet, check out the [installation](/docs/installation).
+
+<Callout type="info">
+The NestJS integration is **community maintained**. If you encounter any issues, please open them at [nestjs-better-auth](https://github.com/ThallesP/nestjs-better-auth).
+</Callout>
+
+## Installation
+
+Install the NestJS integration library:
+
+```package-install
+@thallesp/nestjs-better-auth
+```
+
+## Basic Setup
+
+<Callout type="warn">
+Currently, Better Auth's NestJS integration **only supports Express** and does not work with Fastify.
+</Callout>
+
+### 1. Disable Body Parser
+
+Disable NestJS's built-in body parser to allow Better Auth to handle the raw request body:
+
+```ts title="main.ts"
+import { NestFactory } from "@nestjs/core";
+import { AppModule } from "./app.module";
+
+async function bootstrap() {
+  const app = await NestFactory.create(AppModule, {
+    bodyParser: false, // Required for Better Auth
+  });
+  await app.listen(process.env.PORT ?? 3000);
+}
+bootstrap();
+```
+
+### 2. Import AuthModule
+
+Import the `AuthModule` in your root module:
+
+```ts title="app.module.ts"
+import { Module } from '@nestjs/common';
+import { AuthModule } from '@thallesp/nestjs-better-auth';
+import { auth } from "./auth"; // Your Better Auth instance
+
+@Module({
+  imports: [
+    AuthModule.forRoot(auth),
+  ],
+})
+export class AppModule {}
+```
+
+### 3. Protect Routes
+
+Use the `AuthGuard` to protect your routes:
+
+```ts title="user.controller.ts"
+import { Controller, Get, UseGuards } from '@nestjs/common';
+import { AuthGuard, Session, UserSession } from '@thallesp/nestjs-better-auth';
+
+@Controller('users')
+@UseGuards(AuthGuard)
+export class UserController {
+  @Get('me')
+  async getProfile(@Session() session: UserSession) {
+    return { user: session.user };
+  }
+}
+```
+
+## Full Documentation
+
+For comprehensive documentation including decorators, hooks, global guards, and advanced configuration, visit the [NestJS Better Auth repository](https://github.com/thallesp/nestjs-better-auth).