Pass configured/auth headers to a Datasource.

In some setups (ex openshift), the Datasource will require Grafana
to pass oauth token as header when sending queries.
Also, this PR allow to send any header which is something
Grafana currently does not support.

pkg/api/pluginproxy/ds_proxy_test.go

@@ -8,6 +8,7 @@ import (
 	macaron "gopkg.in/macaron.v1"
 
 	"github.com/grafana/grafana/pkg/components/simplejson"
+	"github.com/grafana/grafana/pkg/log"
 	m "github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/plugins"
 	"github.com/grafana/grafana/pkg/setting"
@@ -212,5 +213,36 @@ func TestDSRouteRule(t *testing.T) {
 			So(interpolated, ShouldEqual, "0asd+asd")
 		})
 
+		Convey("When proxying a data source with custom headers specified", func() {
+			plugin := &plugins.DataSourcePlugin{}
+
+			encryptedData, err := util.Encrypt([]byte(`Bearer xf5yhfkpsnmgo`), setting.SecretKey)
+			ds := &m.DataSource{
+				Type: m.DS_PROMETHEUS,
+				Url:  "http://prometheus:9090",
+				JsonData: simplejson.NewFromAny(map[string]interface{}{
+					"httpHeaderName1": "Authorization",
+				}),
+				SecureJsonData: map[string][]byte{
+					"httpHeaderValue1": encryptedData,
+				},
+			}
+
+			ctx := &m.ReqContext{}
+			proxy := NewDataSourceProxy(ds, plugin, ctx, "")
+
+			requestURL, _ := url.Parse("http://grafana.com/sub")
+			req := http.Request{URL: requestURL, Header: make(http.Header)}
+			proxy.getDirector()(&req)
+
+			if err != nil {
+				log.Fatal(4, err.Error())
+			}
+
+			Convey("Match header value after decryption", func() {
+				So(req.Header.Get("Authorization"), ShouldEqual, "Bearer xf5yhfkpsnmgo")
+			})
+		})
+
 	})
 }