Use Data frames response format (#1099)

* Use data frames for numeric data

* Use data frames for text data

* Use data frames for IT services

* fix multiple series

* Convert to the wide format if possible

* Fix table format for text data

* Add refId to the data frames

* Align time series from Zabbix API

* Fill gaps with nulls

* Fix moving average functions

* Option for disabling data alignment

* remove unused logging

* Add labels to data frames

* Detect units

* Set min and max for if percent unit used

* Use value mapping from Zabbix

* Rename unitConverter -> convertZabbixUnit

* More units

* Add missing points in front of each series

* Fix handling table data

* fix db connector data frames handling

* fix it services data frames handling

* Detect all known grafana units

* Chore: remove unused logging

* Fix problems format

* Debug logging: show original units

* Add global option for disabling data alignment

* Add tooltip for the disableDataAlignment feature

* Add note about query options

* Functions for aligning timeseries on the backend

pkg/datasource/response_handler.go

@@ -0,0 +1,49 @@
+package datasource
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana-plugin-sdk-go/data"
+)
+
+func convertHistory(history History, items Items) *data.Frame {
+	timeFileld := data.NewFieldFromFieldType(data.FieldTypeTime, 0)
+	timeFileld.Name = "time"
+	frame := data.NewFrame("History", timeFileld)
+
+	for _, item := range items {
+		field := data.NewFieldFromFieldType(data.FieldTypeNullableFloat64, 0)
+		if len(item.Hosts) > 0 {
+			field.Name = fmt.Sprintf("%s: %s", item.Hosts[0].Name, item.ExpandItem())
+		} else {
+			field.Name = item.ExpandItem()
+		}
+		frame.Fields = append(frame.Fields, field)
+	}
+
+	for _, point := range history {
+		for columnIndex, field := range frame.Fields {
+			if columnIndex == 0 {
+				ts := time.Unix(point.Clock, point.NS)
+				field.Append(ts)
+			} else {
+				item := items[columnIndex-1]
+				if point.ItemID == item.ID {
+					value := point.Value
+					field.Append(&value)
+				} else {
+					field.Append(nil)
+				}
+			}
+		}
+	}
+
+	wideFrame, err := data.LongToWide(frame, &data.FillMissing{Mode: data.FillModeNull})
+	if err != nil {
+		backend.Logger.Debug("Error converting data frame to the wide format", "error", err)
+		return frame
+	}
+	return wideFrame
+}