FEATURE: Show "Recently used devices" in user preferences (#6335)

* FEATURE: Added MaxMindDb to resolve IP information.

* FEATURE: Added browser detection based on user agent.

* FEATURE: Added recently used devices in user preferences.

* DEV: Added acceptance test for recently used devices.

* UX: Do not show 'Show more' button if there aren't more tokens.

* DEV: Fix unit tests.

* DEV: Make changes after code review.

* Add more detailed unit tests.

* Improve logging messages.

* Minor coding style fixes.

* DEV: Use DropdownSelectBoxComponent and run Prettier.

* DEV: Fix unit tests.

lib/discourse_ip_info.rb

@@ -0,0 +1,46 @@
+require_dependency 'maxminddb'
+
+class DiscourseIpInfo
+  include Singleton
+
+  def initialize
+    begin
+      @mmdb_filename = File.join(Rails.root, 'vendor', 'data', 'GeoLite2-City.mmdb')
+      @mmdb = MaxMindDB.new(@mmdb_filename, MaxMindDB::LOW_MEMORY_FILE_READER)
+      @cache = LruRedux::ThreadSafeCache.new(1000)
+    rescue Errno::ENOENT => e
+      Rails.logger.warn("MaxMindDB could not be found: #{e}")
+    rescue
+      Rails.logger.warn("MaxMindDB could not be loaded.")
+    end
+  end
+
+  def lookup(ip)
+    return {} unless @mmdb
+
+    begin
+      result = @mmdb.lookup(ip)
+    rescue
+      Rails.logger.error("IP #{ip} could not be looked up in MaxMindDB.")
+    end
+
+    return {} if !result || !result.found?
+
+    {
+      country: result.country.name,
+      country_code: result.country.iso_code,
+      region: result.subdivisions.most_specific.name,
+      city: result.city.name,
+    }
+  end
+
+  def get(ip)
+    return {} unless @mmdb
+
+    @cache[ip] ||= lookup(ip)
+  end
+
+  def self.get(ip)
+    instance.get(ip)
+  end
+end