module DeviseTokenAuth::Concerns::TokensSerialization

def dump(object)
  JSON.generate(object && object.transform_values do |token|
    serialize_updated_at(token).compact
  end.compact)
end

def load(json)
  case json
  when String
    JSON.parse(json)
  when NilClass
    {}
  else
    json
  end
end

def serialize_updated_at(token)
  updated_at_key = ['updated_at', :updated_at].find(&token.method(:[]))
  return token unless token[updated_at_key].respond_to?(:iso8601)
  token.merge updated_at_key => token[updated_at_key].iso8601
end