refactor the main structure

src/api/error.rs

@@ -0,0 +1,9 @@
+use derive_more::{Display, Error};
+
+impl actix_web::error::ResponseError for ReturnedError{}
+
+#[derive(Debug, Display, Error)]
+#[display(fmt = "my error: {}", name)]
+pub struct ReturnedError {
+    pub name: String,
+}