added the custom icon and username for the outgoing webhook and its response (#9141)

* 8272 added the username and icon as part of the model and persisted the same

* 8272 added the custome icon and name when set to the web hook response

* 8272 changed the infinte loop to timeout after 5 seconds

* 8272  fixed review comments

app/webhook.go

@@ -133,7 +133,13 @@ func (a *App) TriggerWebhook(payload *model.OutgoingWebhookPayload, hook *model.
 						if len(webhookResp.Attachments) > 0 {
 							webhookResp.Props["attachments"] = webhookResp.Attachments
 						}
+						if a.Config().ServiceSettings.EnablePostUsernameOverride && hook.Username != "" && webhookResp.Username == "" {
+							webhookResp.Username = hook.Username
+						}
 
+						if a.Config().ServiceSettings.EnablePostIconOverride && hook.IconURL != "" && webhookResp.IconURL == "" {
+							webhookResp.IconURL = hook.IconURL
+						}
 						if _, err := a.CreateWebhookPost(hook.CreatorId, channel, text, webhookResp.Username, webhookResp.IconURL, webhookResp.Props, webhookResp.Type, postRootId); err != nil {
 							mlog.Error(fmt.Sprintf("Failed to create response post, err=%v", err))
 						}