Datasource: Shared HTTP client provider for core backend data sources and any data source using the data source proxy (#33439)

Uses new httpclient package from grafana-plugin-sdk-go introduced 
via grafana/grafana-plugin-sdk-go#328. 
Replaces the GetHTTPClient, GetTransport, GetTLSConfig methods defined 
on DataSource model.
Longer-term the goal is to migrate core HTTP backend data sources to use the 
SDK contracts and using httpclient.Provider for creating HTTP clients and such.

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/tsdb/loki/loki.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
+	"github.com/grafana/grafana/pkg/infra/httpclient"
 	"github.com/grafana/grafana/pkg/infra/log"
 	"github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/plugins"
@@ -23,16 +24,17 @@ import (
 
 type LokiExecutor struct {
 	intervalCalculator interval.Calculator
+	httpClientProvider httpclient.Provider
 }
 
-//nolint: staticcheck // plugins.DataPlugin deprecated
-func NewExecutor(dsInfo *models.DataSource) (plugins.DataPlugin, error) {
-	return newExecutor(), nil
-}
-
-func newExecutor() *LokiExecutor {
-	return &LokiExecutor{
-		intervalCalculator: interval.NewCalculator(interval.CalculatorOptions{MinInterval: time.Second * 1}),
+// nolint:staticcheck // plugins.DataPlugin deprecated
+func New(httpClientProvider httpclient.Provider) func(dsInfo *models.DataSource) (plugins.DataPlugin, error) {
+	// nolint:staticcheck // plugins.DataPlugin deprecated
+	return func(dsInfo *models.DataSource) (plugins.DataPlugin, error) {
+		return &LokiExecutor{
+			intervalCalculator: interval.NewCalculator(interval.CalculatorOptions{MinInterval: time.Second * 1}),
+			httpClientProvider: httpClientProvider,
+		}, nil
 	}
 }
 
@@ -49,12 +51,12 @@ func (e *LokiExecutor) DataQuery(ctx context.Context, dsInfo *models.DataSource,
 		Results: map[string]plugins.DataQueryResult{},
 	}
 
-	tlsConfig, err := dsInfo.GetTLSConfig()
+	tlsConfig, err := dsInfo.GetTLSConfig(e.httpClientProvider)
 	if err != nil {
 		return plugins.DataResponse{}, err
 	}
 
-	transport, err := dsInfo.GetHttpTransport()
+	transport, err := dsInfo.GetHTTPTransport(e.httpClientProvider)
 	if err != nil {
 		return plugins.DataResponse{}, err
 	}

pkg/tsdb/loki/loki_test.go

@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/grafana/grafana/pkg/components/simplejson"
+	"github.com/grafana/grafana/pkg/infra/httpclient"
 	"github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/plugins"
 	"github.com/grafana/loki/pkg/loghttp"
@@ -60,9 +61,10 @@ func TestLoki(t *testing.T) {
 			TimeRange: &timeRange,
 		}
 
-		exe := newExecutor()
+		exe, err := New(httpclient.NewProvider())(dsInfo)
 		require.NoError(t, err)
-		models, err := exe.parseQuery(dsInfo, queryContext)
+		lokiExecutor := exe.(*LokiExecutor)
+		models, err := lokiExecutor.parseQuery(dsInfo, queryContext)
 		require.NoError(t, err)
 		require.Equal(t, time.Second*30, models[0].Step)
 	})
@@ -82,15 +84,16 @@ func TestLoki(t *testing.T) {
 				{Model: jsonModel},
 			},
 		}
-		exe := newExecutor()
+		exe, err := New(httpclient.NewProvider())(dsInfo)
 		require.NoError(t, err)
-		models, err := exe.parseQuery(dsInfo, queryContext)
+		lokiExecutor := exe.(*LokiExecutor)
+		models, err := lokiExecutor.parseQuery(dsInfo, queryContext)
 		require.NoError(t, err)
 		require.Equal(t, time.Minute*2, models[0].Step)
 
 		timeRange = plugins.NewDataTimeRange("1h", "now")
 		queryContext.TimeRange = &timeRange
-		models, err = exe.parseQuery(dsInfo, queryContext)
+		models, err = lokiExecutor.parseQuery(dsInfo, queryContext)
 		require.NoError(t, err)
 		require.Equal(t, time.Second*2, models[0].Step)
 	})