Fix #16107
* Optimize map { ... }.compact using Enumerable#filter_map, supported since Ruby 2.7 * Add poyfill for Enumerable#filter_map
* Fix admin validation being too strict about usernames Fix #10446 * Strip Setting.site_contact_username consistently throughout the codebase
* Add validations to admin settings - Validate correct HTML markup - Validate presence of contact username & e-mail - Validate that all usernames are valid - Validate that enums have expected values * Fix code style issue * Fix tests