Add a base struct for api error responses (#524)

Co-authored-by: Sanchith Hegde <22217505+SanchithHegde@users.noreply.github.com>

crates/api_models/src/errors/actix.rs

@@ -0,0 +1,28 @@
+use super::types::ApiErrorResponse;
+
+impl actix_web::ResponseError for ApiErrorResponse {
+    fn status_code(&self) -> reqwest::StatusCode {
+        use reqwest::StatusCode;
+
+        match self {
+            Self::Unauthorized(_) => StatusCode::UNAUTHORIZED,
+            Self::ForbiddenCommonResource(_) => StatusCode::FORBIDDEN,
+            Self::ForbiddenPrivateResource(_) => StatusCode::NOT_FOUND,
+            Self::Conflict(_) => StatusCode::CONFLICT,
+            Self::Gone(_) => StatusCode::GONE,
+            Self::Unprocessable(_) => StatusCode::UNPROCESSABLE_ENTITY,
+            Self::InternalServerError(_) => StatusCode::INTERNAL_SERVER_ERROR,
+            Self::NotImplemented(_) => StatusCode::NOT_IMPLEMENTED,
+            Self::ConnectorError(_, code) => *code,
+        }
+    }
+
+    fn error_response(&self) -> actix_web::HttpResponse {
+        use actix_web::http::header;
+
+        actix_web::HttpResponseBuilder::new(self.status_code())
+            .insert_header((header::CONTENT_TYPE, mime::APPLICATION_JSON))
+            .insert_header((header::VIA, "Juspay_Router"))
+            .body(self.to_string())
+    }
+}