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

api4/webhook_test.go

@@ -256,7 +256,7 @@ func TestCreateOutgoingWebhook(t *testing.T) {
 	th.AddPermissionToRole(model.PERMISSION_MANAGE_WEBHOOKS.Id, model.TEAM_ADMIN_ROLE_ID)
 	th.RemovePermissionFromRole(model.PERMISSION_MANAGE_WEBHOOKS.Id, model.TEAM_USER_ROLE_ID)
 
-	hook := &model.OutgoingWebhook{ChannelId: th.BasicChannel.Id, TeamId: th.BasicChannel.TeamId, CallbackURLs: []string{"http://nowhere.com"}}
+	hook := &model.OutgoingWebhook{ChannelId: th.BasicChannel.Id, TeamId: th.BasicChannel.TeamId, CallbackURLs: []string{"http://nowhere.com"}, Username: "some-user-name", IconURL: "http://some-icon-url/"}
 
 	rhook, resp := th.SystemAdminClient.CreateOutgoingWebhook(hook)
 	CheckNoError(t, resp)