QueryService: Return application/json and better errors (#84234)

pkg/registry/apis/query/errors_test.go

@@ -0,0 +1,21 @@
+package query_test
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/grafana/grafana/pkg/expr"
+	"github.com/grafana/grafana/pkg/util/errutil"
+)
+
+func TestQueryErrorType(t *testing.T) {
+	qet := expr.QueryError
+	utilError := errutil.Error{}
+	qe := expr.MakeQueryError("A", "", fmt.Errorf("not work"))
+
+	require.True(t, errors.Is(qe, qet))
+	require.True(t, errors.As(qe, &utilError))
+}