Move serializers pagination class to separate module

app/serializers/environment_serializer.rb

@@ -8,7 +8,7 @@ class EnvironmentSerializer < BaseSerializer
   end
 
   def with_pagination(request, response)
-    tap { @paginator = Paginator.new(request, response) }
+    tap { @paginator = Gitlab::Serializer::Pagination.new(request, response) }
   end
 
   def itemized?

app/serializers/pipeline_serializer.rb

@@ -4,7 +4,7 @@ class PipelineSerializer < BaseSerializer
   entity PipelineEntity
 
   def with_pagination(request, response)
-    tap { @paginator = Paginator.new(request, response) }
+    tap { @paginator = Gitlab::Serializer::Pagination.new(request, response) }
   end
 
   def paginated?

app/serializers/paginator.rb → lib/gitlab/serializer/pagination.rb

-class Paginator
-  include API::Helpers::Pagination
+module Gitlab
+  module Serializer
+    class Pagination
+      include ::API::Helpers::Pagination
 
       def initialize(request, response)
         @request = request
@@ -20,4 +22,6 @@ class Paginator
       def header(header, value)
         @response.headers[header] = value
       end
+    end
+  end
 end