docs(transactional-adapter-mongoose): add docs

docs/docs/06_plugins/01_available-plugins/01-transactional/07-mongoose-adapter.md

@@ -0,0 +1,119 @@
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
+# Mongoose adapter
+
+## Installation
+
+<Tabs>
+<TabItem value="npm" label="npm" default>
+
+```bash
+npm install @nestjs-cls/transactional-adapter-mongoose
+```
+
+</TabItem>
+<TabItem value="yarn" label="yarn">
+
+```bash
+yarn add @nestjs-cls/transactional-adapter-mongoose
+```
+
+</TabItem>
+<TabItem value="pnpm" label="pnpm">
+
+```bash
+pnpm add @nestjs-cls/transactional-adapter-mongoose
+```
+
+</TabItem>
+</Tabs>
+
+## Registration
+
+```ts
+ClsModule.forRoot({
+    plugins: [
+        new ClsPluginTransactional({
+            imports: [
+                // module in which the Connection instance is provided
+                MongooseModule,
+            ],
+            adapter: new TransactionalAdapterMongoose({
+                // the injection token of the mongoose Connection
+                mongooseConnectionToken: Connection,
+            }),
+        }),
+    ],
+});
+```
+
+## Typing & usage
+
+To work correctly, the adapter needs to inject an instance of mongoose [`Connection`](<https://mongoosejs.com/docs/api/connection.html#Connection()>).
+
+Due to how transactions work in MongoDB, [and in turn in Mongoose](https://mongoosejs.com/docs/transactions.html), the usage of the Mongoose adapter is a bit different from the others.
+
+The `tx` property on the `TransactionHost<TransactionalAdapterMongoose>` does _not_ refer to any _transactional_ instance, but rather to a [`ClientSession`](https://mongodb.github.io/node-mongodb-native/6.7/classes/ClientSession.html) instance of `mongodb`, with an active transaction, or `null` when no transaction is active.
+
+Queries are not executed using the `ClientSession` instance, but instead the `ClientSession` instance or `null` is passed to the query as the `session` option.
+
+:::important
+
+The `TransactionalAdapterMongoose` _does not support_ the ["Transaction Proxy"](./index.md#using-the-injecttransaction-decorator) feature, because proxying a `null` value is not supported by the JavaScript Proxy.
+
+::::
+
+## Example
+
+```ts title="database.schemas.ts"
+const userSchema = new Schema({
+    name: String,
+    email: String,
+});
+
+const User = mongoose.model('user', userSchema);
+```
+
+```ts title="user.service.ts"
+@Injectable()
+class UserService {
+    constructor(private readonly userRepository: UserRepository) {}
+
+    @Transactional()
+    async runTransaction() {
+        // highlight-start
+        // both methods are executed in the same transaction
+        const user = await this.userRepository.createUser('John');
+        const foundUser = await this.userRepository.getUserById(user._id);
+        // highlight-end
+        assert(foundUser._id === user._id);
+    }
+}
+```
+
+```ts title="user.repository.ts"
+@Injectable()
+class UserRepository {
+    constructor(
+        private readonly txHost: TransactionHost<TransactionalAdapterMongoose>,
+    ) {}
+
+    async getUserById(id: ObjectId) {
+        // txHost.tx is typed as ClientSession
+        return await User.findById(id)
+            // highlight-start
+            .session(this.txHost.tx);
+        // highlight-end
+    }
+
+    async createUser(name: string) {
+        const user = new User({ name: name, email: `${name}@email.com` });
+        await user
+            // highlight-start
+            .save({ session: this.txHost.tx });
+        // highlight-end
+        return user;
+    }
+}
+```

packages/transactional-adapters/transactional-adapter-mongoose/src/lib/transactional-adapter-mongoose.ts

@@ -49,6 +49,8 @@ export class TransactionalAdapterMongoose
         }
     }
 
+    supportsTransactionProxy = false;
+
     optionsFactory(connection: Connection) {
         return {
             wrapWithTransaction: async (