datasources: querier: better handling of timestamps (#108973)

* query: support query-local timestamps

* make it configurable

* lint fix

* corrected unit test

* fixed unit test

pkg/expr/query_convert_test.go

@@ -0,0 +1,50 @@
+package expr
+
+import (
+	"testing"
+	"time"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	data "github.com/grafana/grafana-plugin-sdk-go/experimental/apis/data/v0alpha1"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConvertBackendRequestToDataRequest(t *testing.T) {
+	input1 := backend.DataQuery{
+		RefID:         "A",
+		QueryType:     "large",
+		MaxDataPoints: 42,
+		Interval:      time.Millisecond * 10,
+		TimeRange: backend.TimeRange{
+			From: time.UnixMilli(1753959290000),
+			To:   time.UnixMilli(1753959390000),
+		},
+		JSON: []byte(`{ "field1": "value1" }`),
+	}
+
+	result1 := data.DataQuery{
+		CommonQueryProperties: data.CommonQueryProperties{
+			RefID:         "A",
+			QueryType:     "large",
+			MaxDataPoints: 42,
+			IntervalMS:    10.0,
+			TimeRange: &data.TimeRange{
+				From: "1753959290000",
+				To:   "1753959390000",
+			},
+		},
+	}
+	result1.Set("field1", "value1")
+
+	req := backend.QueryDataRequest{
+		Queries: []backend.DataQuery{input1},
+	}
+
+	expected := data.QueryDataRequest{
+		Queries: []data.DataQuery{result1},
+	}
+
+	result, err := ConvertBackendRequestToDataRequest(&req)
+	require.NoError(t, err)
+	require.Equal(t, &expected, result)
+}