Cloudwatch: Refactor dimension values resource request (#57346)

* refactor dimension values backend

* fix test file name

pkg/tsdb/cloudwatch/models/request/utils.go

@@ -0,0 +1,44 @@
+package request
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+func parseDimensionFilter(dimensionFilter string) ([]*Dimension, error) {
+	dimensionFilters := map[string]interface{}{}
+	dimensionFilterJson := []byte(dimensionFilter)
+	if len(dimensionFilterJson) > 0 {
+		err := json.Unmarshal(dimensionFilterJson, &dimensionFilters)
+		if err != nil {
+			return nil, fmt.Errorf("error unmarshaling dimensionFilters: %v", err)
+		}
+	}
+
+	dimensions := []*Dimension{}
+	addDimension := func(key string, value string) {
+		d := &Dimension{
+			Name: key,
+		}
+		// if value is not specified or a wildcard is used, simply don't use the value field
+		if value != "" && value != "*" {
+			d.Value = value
+		}
+		dimensions = append(dimensions, d)
+	}
+
+	for k, v := range dimensionFilters {
+		// due to legacy, value can be a string, a string slice or nil
+		if vv, ok := v.(string); ok {
+			addDimension(k, vv)
+		} else if vv, ok := v.([]interface{}); ok {
+			for _, v := range vv {
+				addDimension(k, v.(string))
+			}
+		} else if v == nil {
+			addDimension(k, "")
+		}
+	}
+
+	return dimensions, nil
+}