email_notif_for_new_users is ignored when creating new users via the Admin API #7135

Description

I created a few uses via the Synapse Admin API using the new threepids option to assign email addresses. I noticed though that the new users don't receive push notifications via the configured email address, despite having the notif_for_new_users configuration option set.

Steps to reproduce

• run a synapse server with setting notif_for_new_users: true (the default) and a working email configuration
• Create a new user via the “Create or modify Account” Admin API

PUT /_synapse/admin/v2/users/testuser
{
    "password": "testuser_password",
    "threepids": [
        {
            "medium": "email",
            "address": "testuser@example.org"
        }
    ]
}

• login as testuser
• see that the email address is present in the user settings
• see that email notifications for the address however are disabled in the user notification settings

Relevant Code Sections in v1.12.0

• notif_for_new_users setting

• email_notif_for_new_users check on interactive registration

• missing check in user admin API somewhere around here

Version information

• Homeserver: self-hosted

• Version: 1.12.0

• Install method: package manager

• Platform: NixOS 19.03