InfluxDB: Fix sending retention policy with the backend request (#72763)

* Add retention policy to the request

* refactor

* refactor influxql query flow

* fix healthcheck

* organize imports

* handle queries separately

* fix tests

* update bench test

pkg/tsdb/influxdb/models/query_part_test.go

@@ -0,0 +1,44 @@
+package models
+
+import (
+	"testing"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+)
+
+func TestInfluxdbQueryPart(t *testing.T) {
+	tcs := []struct {
+		mode     string
+		input    string
+		params   []string
+		expected string
+	}{
+		{mode: "field", params: []string{"value"}, input: "value", expected: `"value"`},
+		{mode: "derivative", params: []string{"10s"}, input: "mean(value)", expected: `derivative(mean(value), 10s)`},
+		{mode: "bottom", params: []string{"3"}, input: "value", expected: `bottom(value, 3)`},
+		{mode: "time", params: []string{"$interval"}, input: "", expected: `time($interval)`},
+		{mode: "time", params: []string{"auto"}, input: "", expected: `time($__interval)`},
+		{mode: "spread", params: []string{}, input: "value", expected: `spread(value)`},
+		{mode: "math", params: []string{"/ 100"}, input: "mean(value)", expected: `mean(value) / 100`},
+		{mode: "alias", params: []string{"test"}, input: "mean(value)", expected: `mean(value) AS "test"`},
+		{mode: "count", params: []string{}, input: "distinct(value)", expected: `count(distinct(value))`},
+		{mode: "mode", params: []string{}, input: "value", expected: `mode(value)`},
+		{mode: "cumulative_sum", params: []string{}, input: "mean(value)", expected: `cumulative_sum(mean(value))`},
+		{mode: "non_negative_difference", params: []string{}, input: "max(value)", expected: `non_negative_difference(max(value))`},
+	}
+
+	queryContext := &backend.QueryDataRequest{}
+	query := &Query{}
+
+	for _, tc := range tcs {
+		part, err := NewQueryPart(tc.mode, tc.params)
+		if err != nil {
+			t.Errorf("Expected NewQueryPart to not return an error. error: %v", err)
+		}
+
+		res := part.Render(query, queryContext, tc.input)
+		if res != tc.expected {
+			t.Errorf("expected %v to render into %s", tc, tc.expected)
+		}
+	}
+}