Move Geo tracking database connection into a concern

app/models/geo/base_fdw.rb

 class Geo::BaseFdw < ActiveRecord::Base
-  self.abstract_class = true
-
-  if Gitlab::Geo.geo_database_configured?
-    establish_connection Rails.configuration.geo_database
-  end
+  include ::EE::Geo::GeoTrackable
 
-  def self.connection
-    raise 'Geo secondary database is not configured' unless Gitlab::Geo.geo_database_configured?
-
-    super
-  end
+  self.abstract_class = true
 end

app/models/geo/base_registry.rb

 class Geo::BaseRegistry < ActiveRecord::Base
-  self.abstract_class = true
-
-  if Gitlab::Geo.geo_database_configured?
-    establish_connection Rails.configuration.geo_database
-  end
+  include ::EE::Geo::GeoTrackable
 
-  def self.connection
-    raise 'Geo secondary database is not configured' unless Gitlab::Geo.geo_database_configured?
-
-    super
-  end
+  self.abstract_class = true
 end

app/models/geo/fdw/lfs_object.rb

@@ -5,4 +5,3 @@ module Geo
     end
   end
 end
-

ee/app/models/concerns/ee/geo/geo_trackable.rb

+module EE
+  module Geo
+    module GeoTrackable
+      extend ActiveSupport::Concern
+
+      included do
+        if ::Gitlab::Geo.geo_database_configured?
+          establish_connection Rails.configuration.geo_database
+        end
+      end
+
+      class_methods do
+        def self.connection
+          raise 'Geo secondary database is not configured' unless ::Gitlab::Geo.geo_database_configured?
+
+          super
+        end
+      end
+    end
+  end
+end