Add back consumeAndClose functionality. (#7608)

* consume bodies for action button integrations, webrtc gateway, oauth
endpoint

* Fixing a couple more places, switching to io.Copy to ioutil.Discard, adding a comment to help prevent future performance regressions

app/oauth.go

@@ -685,7 +685,7 @@ func (a *App) AuthorizeOAuthUser(w http.ResponseWriter, r *http.Request, service
 		return nil, "", stateProps, model.NewAppError("AuthorizeOAuthUser", "api.user.authorize_oauth_user.token_failed.app_error", nil, err.Error(), http.StatusInternalServerError)
 	} else {
 		ar = model.AccessResponseFromJson(resp.Body)
-		resp.Body.Close()
+		consumeAndClose(resp)
 
 		if ar == nil {
 			return nil, "", stateProps, model.NewAppError("AuthorizeOAuthUser", "api.user.authorize_oauth_user.bad_response.app_error", nil, "response_body="+string(bodyBytes), http.StatusInternalServerError)