docs: Fix `#[SimpleObject]` in federation examples
@@ -133,7 +133,7 @@ Apply the [`@shareable` directive](https://www.apollographql.com/docs/federation
```rust
# extern crate async_graphql;
# use async_graphql::*;
-#[SimpleObject]
+#[derive(SimpleObject)]
#[graphql(complex)]
struct Position {
#[graphql(shareable)]
@@ -164,7 +164,7 @@ type Position {
```rust
# extern crate async_graphql;
# use async_graphql::*;
-#[SimpleObject]
+#[derive(SimpleObject)]
#[graphql(shareable)]
struct Position {
x: u64,
@@ -188,7 +188,7 @@ The [`@inaccessible` directive](https://www.apollographql.com/docs/federation/fe
```rust
# extern crate async_graphql;
# use async_graphql::*;
-#[SimpleObject]
+#[derive(SimpleObject)]
#[graphql(shareable)]
struct Position {
x: u32,
@@ -217,7 +217,7 @@ For example, if you add a new "Inventory" subgraph which should take over respon
```rust
# extern crate async_graphql;
# use async_graphql::*;
-#[SimpleObject]
+#[derive(SimpleObject)]
struct Product {
id: ID,
#[graphql(override_from = "Products")]
@@ -241,7 +241,7 @@ The [`@external` directive](https://www.apollographql.com/docs/federation/federa
```rust
# extern crate async_graphql;
# use async_graphql::*;
-#[SimpleObject]
+#[derive(SimpleObject)]
struct Product {
id: ID,
#[graphql(external)]
@@ -267,7 +267,7 @@ The [`@provides` directive](https://www.apollographql.com/docs/federation/federa
```rust
# extern crate async_graphql;
# use async_graphql::*;
-#[SimpleObject]
+#[derive(SimpleObject)]
struct Product {
id: ID,
#[graphql(external)]
@@ -341,7 +341,7 @@ In order to implement this in Rust, we can use the `#[graphql(requires)]` attrib
```rust
# extern crate async_graphql;
# use async_graphql::*;
-#[SimpleObject]
+#[derive(SimpleObject)]
#[graphql(complex)]
struct Product {
id: ID,
@@ -366,7 +366,7 @@ Note that we use the GraphQL field name `weightInPounds`, not the Rust field nam
```rust
# extern crate async_graphql;
# use async_graphql::*;
-# #[SimpleObject]
+# #[derive(SimpleObject)]
# #[graphql(complex)]
# struct Product {
# id: ID,
@@ -435,7 +435,7 @@ You can write code like this:
```rust
# extern crate async_graphql;
# use async_graphql::*;
-#[SimpleObject]
+#[derive(SimpleObject)]
#[graphql(tag = "team-accounts")]
struct User {
id: ID,
