feat: improve error log and add flag disabled handling for ofrep (#1306)

## This PR

- Handle `FlagDisabledErrorCode` and include a specific error message
along with general error code
- Improve error message for targeting rule validation failure

---------

Signed-off-by: Kavindu Dodanduwa <kavindudodanduwa@gmail.com>

core/pkg/evaluator/json.go

@@ -376,7 +376,7 @@ func (je *Resolver) evaluateVariant(ctx context.Context, reqID string, flagKey s
 		// evaluate JsonLogic rules to determine the variant
 		err = jsonlogic.Apply(bytes.NewReader(targetingBytes), bytes.NewReader(b), &result)
 		if err != nil {
-			je.Logger.ErrorWithID(reqID, fmt.Sprintf("error applying rules: %s", err))
+			je.Logger.ErrorWithID(reqID, fmt.Sprintf("error applying targeting rules: %s", err))
 			return "", flag.Variants, model.ErrorReason, metadata, errors.New(model.ParseErrorCode)
 		}
 

core/pkg/service/ofrep/models.go

@@ -92,6 +92,10 @@ func EvaluationErrorResponseFrom(result evaluator.AnyValue) (int, EvaluationErro
 		status = 404
 		payload.ErrorCode = model.FlagNotFoundErrorCode
 		payload.ErrorDetails = fmt.Sprintf("flag `%s` does not exist", result.FlagKey)
+	case model.FlagDisabledErrorCode:
+		status = 404
+		payload.ErrorCode = model.FlagNotFoundErrorCode
+		payload.ErrorDetails = fmt.Sprintf("flag `%s` is disabled", result.FlagKey)
 	case model.ParseErrorCode:
 		payload.ErrorCode = model.ParseErrorCode
 		payload.ErrorDetails = fmt.Sprintf("error parsing the flag `%s`", result.FlagKey)

core/pkg/service/ofrep/models_test.go

@@ -89,8 +89,8 @@ func TestErrorStatus(t *testing.T) {
 		{
 			name:           "flag disabled",
 			modelError:     model.FlagDisabledErrorCode,
-			expectedStatus: 400,
-			expectedCode:   model.GeneralErrorCode,
+			expectedStatus: 404,
+			expectedCode:   model.FlagNotFoundErrorCode,
 		},
 		{
 			name:           "general error",