Night mode is an automatic setting which takes advantage of the new wide-angle camera that's in the iPhone 11 and 11 Pro models. It's equipped with a larger sensor that is able to let in more light, allowing for brighter photos when the light is low.
macOS Catalina Now Available
TestFlight Experiencing Extended Downtime for Many Developers
Apple has yet to update its system status page for developers to reflect the outage, although the company has historically been rather delayed at doing so. The outage has been confirmed to be affecting developers in the United States, Canada and Europe, and likely elsewhere, preventing developers from seeding pre-release versions of their apps for testing for the meantime.