Add login

Fields sent are

```
{
  "query": "mutation Login($input: LoginCredentials!) { login(input: $input) { accessToken tokenType } }",
  "variables": {
    "input": {
      "email": "....",
      "password": "..."
    }
  }
}
```

2 files changed, 80 insertions, 0 deletions

diff --git a/src/graphql/types/jwt.rs b/src/graphql/types/jwt.rs
new file mode 100644
index 0000000..932f7fd
--- /dev/null
+++ b/src/graphql/types/jwt.rs
@@ -0,0 +1,79 @@
+use crate::errors::AppError;
+use async_graphql::{InputObject, SimpleObject};
+use chrono::{Duration, Local};
+use jsonwebtoken::{decode, encode, DecodingKey, EncodingKey, Header, Validation};
+use once_cell::sync::Lazy;
+use serde::{Deserialize, Serialize};
+
+struct Keys {
+    encoding: EncodingKey,
+    _decoding: DecodingKey,
+}
+
+static KEYS: Lazy<Keys> = Lazy::new(|| {
+    let secret = &crate::config::CONFIG.jwt_secret;
+    Keys::new(secret.as_bytes())
+});
+
+impl Keys {
+    fn new(secret: &[u8]) -> Self {
+        Self {
+            encoding: EncodingKey::from_secret(secret),
+            _decoding: DecodingKey::from_secret(secret),
+        }
+    }
+}
+
+/// Claims struct
+#[derive(Serialize, Deserialize)]
+pub struct Claims {
+    /// ID from the user model
+    pub user_id: i32,
+    /// Expiration timestamp
+    exp: usize,
+}
+
+impl Claims {
+    /// Create a new Claim using the `user_id` and the current timestamp + 2 days
+    pub fn new(user_id: i32) -> Self {
+        let expiration = Local::now() + Duration::days(2);
+
+        Self {
+            user_id,
+            exp: expiration.timestamp() as usize,
+        }
+    }
+
+    /// Returns the token as a string. If a token is not encoded, raises an
+    /// `AppError::TokenCreation`
+    pub fn get_token(&self) -> Result<String, AppError> {
+        let token = encode(&Header::default(), &self, &KEYS.encoding)
+            .map_err(|_| AppError::TokenCreation)?;
+
+        Ok(token)
+    }
+}
+
+#[derive(InputObject, Debug)]
+pub struct LoginCredentials {
+    pub email: String,
+    pub password: String,
+}
+
+/// Body used as response to login
+#[derive(Serialize, SimpleObject)]
+pub struct AuthBody {
+    /// Access token string
+    access_token: String,
+    /// "Bearer" string
+    token_type: String,
+}
+
+impl AuthBody {
+    pub fn new(access_token: String) -> Self {
+        Self {
+            access_token,
+            token_type: "Bearer".to_string(),
+        }
+    }
+}
diff --git a/src/graphql/types/mod.rs b/src/graphql/types/mod.rs
index 22d12a3..d7cdece 100644
--- a/src/graphql/types/mod.rs
+++ b/src/graphql/types/mod.rs
@@ -1 +1,2 @@
+pub mod jwt;
 pub mod user;