Add graphql field get_user_id

Given a username it will give you this user's ID

src/graphql.rs

@@ -373,6 +373,16 @@ impl Query {
 
 #[graphql_object(context = Context)]
 impl Query {
+    async fn get_user_id(context: &Context, username: String) -> FieldResult<ID> {
+        sqlx::query(format!(
+            r#"SELECT id FROM users WHERE user_name="{}""#,
+            username
+        ).as_str()).fetch_one(&context.db).await?
+            .try_get::<String, _>("id")
+            .map(ID::new)
+            .map_err(FieldError::from)
+    }
+
     async fn users(context: &Context) -> FieldResult<Vec<User>> {
         Self::users_sqlx_result(context).await.map_err(FieldError::from)
     }