Add overview of active sessions (#3929)

* Add overview of active sessions

* Better display of browser/platform name

* Improve how browser information is stored and displayed for sessions overview

* Fix test

app/models/session_activation.rb

@@ -8,31 +8,49 @@
 #  session_id :string           not null
 #  created_at :datetime         not null
 #  updated_at :datetime         not null
+#  user_agent :string           default(""), not null
+#  ip         :inet
 #
 
 class SessionActivation < ApplicationRecord
-  LIMIT = Rails.configuration.x.max_session_activations
-
-  def self.active?(id)
-    id && where(session_id: id).exists?
+  def detection
+    @detection ||= Browser.new(user_agent)
   end
 
-  def self.activate(id)
-    activation = create!(session_id: id)
-    purge_old
-    activation
+  def browser
+    detection.id
   end
 
-  def self.deactivate(id)
-    return unless id
-    where(session_id: id).destroy_all
+  def platform
+    detection.platform.id
   end
 
-  def self.purge_old
-    order('created_at desc').offset(LIMIT).destroy_all
+  before_save do
+    self.user_agent = '' if user_agent.nil?
   end
 
-  def self.exclusive(id)
-    where('session_id != ?', id).destroy_all
+  class << self
+    def active?(id)
+      id && where(session_id: id).exists?
+    end
+
+    def activate(options = {})
+      activation = create!(options)
+      purge_old
+      activation
+    end
+
+    def deactivate(id)
+      return unless id
+      where(session_id: id).destroy_all
+    end
+
+    def purge_old
+      order('created_at desc').offset(Rails.configuration.x.max_session_activations).destroy_all
+    end
+
+    def exclusive(id)
+      where('session_id != ?', id).destroy_all
+    end
   end
 end