Implement a setting option to disable "Unknown sign-in from new location"

Problem to solve

As a Gitlab administrator I'd like to be able to turn off the "Unknown sign-in from new location" email notification for my instance since my end users may receive this email after every login depending on my Gitlab configuration. The option to manually turn this off would enhance the user experience with Gitlab.

Intended users

Every Gitlab user which receives this kind of e-mails.

Proposal

Implement the option to turn off the notification at the instance level.

Permissions and Security

Administrator only.

Documentation

Availability & Testing