HTTP client refactor (#7884)

* http client refactor

* simplification

app/webhook.go

@@ -106,7 +106,7 @@ func (a *App) TriggerWebhook(payload *model.OutgoingWebhookPayload, hook *model.
 				req, _ := http.NewRequest("POST", url, body)
 				req.Header.Set("Content-Type", contentType)
 				req.Header.Set("Accept", "application/json")
-				if resp, err := utils.HttpClient(false).Do(req); err != nil {
+				if resp, err := a.HTTPClient(false).Do(req); err != nil {
 					l4g.Error(utils.T("api.post.handle_webhook_events_and_forget.event_post.error"), err.Error())
 				} else {
 					defer consumeAndClose(resp)