Use a common base class to centralize access to Geo secondary DB

app/models/geo/base_fdw.rb

-class Geo::BaseFdw < ActiveRecord::Base
-  include ::EE::Geo::GeoTrackable
-
+class Geo::BaseFdw < Geo::TrackingBase
   self.abstract_class = true
 end

app/models/geo/base_registry.rb

-class Geo::BaseRegistry < ActiveRecord::Base
-  include ::EE::Geo::GeoTrackable
-
+class Geo::BaseRegistry < Geo::TrackingBase
   self.abstract_class = true
 end

app/models/geo/tracking_base.rb

+# This module is intended to centralize all database access to the secondary
+# tracking database for Geo. 
+module Geo
+  class TrackingBase < ActiveRecord::Base
+    self.abstract_class = true
+
+    if ::Gitlab::Geo.geo_database_configured?
+      establish_connection Rails.configuration.geo_database
+    end
+
+    def self.connection
+      raise 'Geo secondary database is not configured' unless ::Gitlab::Geo.geo_database_configured?
+
+      super
+    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