style(backend): improve error handling

backend/internal/interfaces/rest/handlers/error_handler.go

@@ -1,7 +1,6 @@
 package rest
 
 import (
-	"fmt"
 	"net/http"
 
 	"tanabata/internal/domain"
@@ -17,28 +16,28 @@ type ErrorMapper struct{}
 
 func (m *ErrorMapper) MapError(err domain.DomainError) (int, ErrorResponse) {
 	switch err.Code {
-	case domain.ErrFileNotFound:
+	case domain.ErrCodeFileNotFound:
 		return http.StatusNotFound, ErrorResponse{
 			Error:   "Not Found",
 			Code:    string(err.Code),
-			Message: fmt.Sprintf("File %q not found", err.Details...),
+			Message: err.Message,
 		}
-	case domain.ErrMIMENotSupported:
+	case domain.ErrCodeMIMENotSupported:
 		return http.StatusNotFound, ErrorResponse{
 			Error:   "MIME not supported",
 			Code:    string(err.Code),
-			Message: fmt.Sprintf("MIME not supported: %q", err.Details...),
+			Message: err.Message,
 		}
-	case domain.ErrValidation:
+	case domain.ErrCodeBadRequest:
 		return http.StatusNotFound, ErrorResponse{
 			Error:   "Bad Request",
 			Code:    string(err.Code),
-			Message: fmt.Sprintf("Invalid %s: %s", err.Details...),
+			Message: err.Message,
 		}
 	}
 	return http.StatusInternalServerError, ErrorResponse{
 		Error:   "Internal Server Error",
 		Code:    string(err.Code),
-		Message: "An unexpected error occured",
+		Message: err.Message,
 	}
 }