User register endpoint showing notifications I'm trying to setup an endpoint for a 3rd party app to allow users to be created on my site through a REST endpoint, which is mostly working so far, although, I've just navigated to my site through the front end, and I've realised it's showing me all the notifications for all the test users I'm creating.

I'm not logged in as an administrator, just a normal user account, and the setting for Show errors and notifications is off, so why is it showing me all these notifications, there's no way I can leave that in
Base on you're working with RESTful API and does not need these messages anymore you can disable them ( all of them or parts of them based on what you don't want) 
by  Disable message module :

Gives a site owner options to disable specific messages shown to end users. The core drupal message system as offered by drupal_set_message is an excellent way for modules to send out messages to the end users. However not all drupal site owners are keen to show all the messages sent out by drupal core and all modules to their users. This module gives site administrators a reasonably powerful way to filter out messages shown to the end users.

Features

Filter out messages that match a full text string exactly.
Filter out messages that match a regular expression.
Permissions to specifically hide all messages of a given type from any role.
Disable all filtering for specific users.
Disable all filtering for specific paths.
Apply filtering only for specific paths.
Debug system to get messages in the HTML without showing it to the end users.


or another solution is  on the theme prevent it got rendered by  this solution : https://www.drupal.org/forum/support/installing-drupal/2011-01-23/how-to-turn-off-error-messages