Feature: two config ways both work

[ZZYhho]

I want to use a redis_exporter to monitor multiple versions of Redis. I typically use non-default users with -redis.user=exporter and -redis.password. However, for Redis versions lower than 6.0, only the default user can be used. Therefore, I am submitting this request: for lower versions of Redis, please allow the use of --redis.password-file, while for other versions, I would like to continue using -redis.user=exporter and -redis.password. the both config ways all work.
example: ./redis_exporter -redis.user=exporter -redis.password=xxx --redis.password-file=./passwd.json