Feature: IP + username for authorization

[shimaore]

Add an option to require both IP-based and username+password-based authorization.

[shimaore]

There are two approaches for this:

• require_both_auth: Two independent records (one for IP, one for username) must be validated, but not correlated. (e.g. user can move devices between authorized IP addresses).
• required_same_auth: IP and username must both match for a single record (username will only validate on a single IP).

[shimaore]

Commit 0b5ffb633ce321f7d619a2fad9a8d4e318acf74e has require_same_auth.