Add a flag for input redis username

[seanhsu17]

Description

We need to use the Redis username to connect to our Redis, but it seems there is no this flag to start asynqmon.
I tried to use the redis-url to start it, but there are some special characters in our password (e.g. @, % etc...) so the parser will parse our password in the wrong way.

Solution

Can I submit a PR to add a flag for --redis-username?

[hibiken]

Sure, please feel free to open a PR

[ChihSeanHsu]

Thanks, I've created a PR for this issue.