Failed attempt at rendering JSON for the rest view

I think something changed for rocket 0.5 becuase rustc is telling me:

```
the trait `Responder<'_, '_>` is not implemented for
  `rocket_contrib::json::Json<Person>`
```

Which I think doesn't make sense. It's their contrib wrapper over serde?
It's versioned ~.4 though so I think I need to bump that.

Cargo.toml

@@ -9,3 +9,10 @@ edition = "2018"
 juniper_rocket = "0.8.0"
 juniper = "0.15.7"
 rocket = "0.5.0-rc.1"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+
+[dependencies.rocket_contrib]
+version = "0.4.10"
+default-features = false
+features = ["json"]

src/model.rs

@@ -1,7 +1,8 @@
 use std::sync::{ atomic::AtomicUsize, atomic::Ordering, Mutex };
 use std::{ collections::HashMap };
+use serde::{Deserialize, Serialize};
 
-#[derive(Clone)]
+#[derive(Clone, Serialize, Deserialize)]
 pub struct Person {
     id: String,
     name: String,

src/rest.rs

@@ -1,12 +1,16 @@
 use rocket::fairing::AdHoc;
 use rocket::State;
-use crate::model::Database;
+use rocket_contrib::json::Json;
+use crate::model::{
+    Database,
+    Person,
+};
 
-#[rocket::get("/rest/<id>")]
+#[rocket::get("/rest/<id>", format = "json")]
-fn get_rest(id: String, context: &State<Database>) -> Option<String> {
+fn get_rest(id: String, context: &State<Database>) -> Option<Json<Person>> {
     match context.get_person(&id) {
         None => None,
-        Some(person) => Some(person.name().unwrap().to_string())
+        Some(person) => Some(Json(person))
     }
 }