Add missing file

lib/bitbucket_server/collection.rb

+module BitbucketServer
+  class Collection < Enumerator
+    def initialize(paginator)
+      super() do |yielder|
+        loop do
+          paginator.items.each { |item| yielder << item }
+        end
+      end
+
+      lazy
+    end
+
+    def method_missing(method, *args)
+      return super unless self.respond_to?(method)
+
+      self.__send__(method, *args) do |item| # rubocop:disable GitlabSecurity/PublicSend
+        block_given? ? yield(item) : item
+      end
+    end
+  end
+end