Enhance error message returned from Loki

Before when getting http status code other than 204,
only the response http headers would get printed.
This commit adds also the body to the log message,
which includes error description sent by Loki.

connector/loki/loki.go

@@ -4,10 +4,12 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net/http"
 	"net/url"
 	"strconv"
+	"strings"
 	"sync"
 	"time"
 
@@ -301,9 +303,17 @@ func (client *LokiConnector) send() (*http.Response, error) {
 	}
 	defer response.Body.Close()
 	if response.StatusCode != 204 {
+		buffer := new(strings.Builder)
+		body := ""
+		_, errCopy := io.Copy(buffer, response.Body)
+		if errCopy == nil {
+			body = buffer.String()
+		}
+
 		client.logger.Metadata(map[string]interface{}{
-			"error":    err,
-			"response": response,
+			"error":            err,
+			"response headers": response,
+			"response body":    body,
 		})
 		client.logger.Error("Recieved unexpected statuscode when trying to send logs")
 		return nil, fmt.Errorf("Got %d http status code after pushing to loki instead of expected 204", response.StatusCode)