Spider.logger not logging custom extra information

[bloodforcream]

I noticed the implicit behavior of the Spider.logger: when logging with extra, extra ultimately do not end up in the log because they are overwritten by default process method of LoggerAdapter

Current logic:

>>> self.logger.info("test log", extra={"test": "very important information"})
{"message": "test log", "spider": "spider_name"}

Expected logic:

>>> self.logger.info("test log", extra={"test": "very important information"})
{"message": "test log", "spider": "spider_name", "test": "very important information"}