docs: move custom message serialization to custom transport page

Author: jmcdo29

content/microservices/basics.md

@@ -371,36 +371,3 @@ this.client
 > info **Hint** The `timeout` operator is imported from the `rxjs/operators` package.
 
 After 5 seconds, if the microservice isn't responding, it will throw an error.
-
-#### Custom Message Serialization
-
-If you need to add some custom logic around the serialization of responses on the client side, you can use a custom class that extends the `ClientProxy` class or one of its child classes. For modifying successful requests you can override the `serializeResponse` method, and for modifying any errors that go through this client you can override the `serializeError` method. To make use of this custom class, you can pass the class itself to the `ClientsModule.register()` method using the `customClass` property. Below is an example of a custom `ClientProxy` that serializes each error into an `RpcException`.
-
-```typescript
-@@filename(error-handling.proxy)
-import { ClientTcp, RpcException } from '@nestjs/microservices';
-
-class ErrorHandlingProxy extends ClientTCP {
-  serializeError(err: Error) {
-    return new RpcException(err);
-  }
-}
-```
-
-and then use it in the `ClientsModule` like so
-
-```typescript
-@@filename(app.module)
-@Module({
-  imports: [
-    ClientsModule.register({
-      name: 'CustomProxy',
-      customClass: ErrorHandlingProxy,
-    }),
-  ]
-})
-export class AppModule
-```
-
-> info **hint** This is the class itself being passed to `customClass`, not an instance of the class. Nest will create the instance under the hood for you, and will pass any options given to the `options` property to the new `ClientProxy`.
-> 

content/microservices/custom-transport.md

@@ -215,3 +215,36 @@ And that's what you should see in the console:
 connect
 event to dispatch:  { pattern: 'event', data: 'Hello world!' }
 ```
+
+#### Message Serialization
+
+If you need to add some custom logic around the serialization of responses on the client side, you can use a custom class that extends the `ClientProxy` class or one of its child classes. For modifying successful requests you can override the `serializeResponse` method, and for modifying any errors that go through this client you can override the `serializeError` method. To make use of this custom class, you can pass the class itself to the `ClientsModule.register()` method using the `customClass` property. Below is an example of a custom `ClientProxy` that serializes each error into an `RpcException`.
+
+```typescript
+@@filename(error-handling.proxy)
+import { ClientTcp, RpcException } from '@nestjs/microservices';
+
+class ErrorHandlingProxy extends ClientTCP {
+  serializeError(err: Error) {
+    return new RpcException(err);
+  }
+}
+```
+
+and then use it in the `ClientsModule` like so
+
+```typescript
+@@filename(app.module)
+@Module({
+  imports: [
+    ClientsModule.register({
+      name: 'CustomProxy',
+      customClass: ErrorHandlingProxy,
+    }),
+  ]
+})
+export class AppModule
+```
+
+> info **hint** This is the class itself being passed to `customClass`, not an instance of the class. Nest will create the instance under the hood for you, and will pass any options given to the `options` property to the new `ClientProxy`.
+>