Feature: Configurable sign-in notifications for internal network

Feature description

Create an option (disabled by default) to mute e-mail notifications about successful sign-ins from the internal network. Provide the information that it requires a properly configured reverse proxy, a geolocation DB setup, and it might decrease the security level.

Pitch

I've got my Pocket ID instance exposed publicly. However, it's rare for me to sign in from outside my home network. Most of the time, I receive email notifications about a "New device login", with the "Approximate location" being properly recognized as "LAN, Internal Network". I want to be notified only about logins from outside my home network, since it happens much less frequently.