Add db_index option to Redis cache configuration

[DeanNeaht]

Description

This PR introduces the db_index option in the Redis cache configuration for chproxy. The feature allows specifying a particular Redis database index for caching

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Checklist

• Linter passes correctly
• Add tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary

Does this introduce a breaking change?

• Yes
• No

[mga-chka]

FYI all the maintainers are off, we'll review the PR in January

[mga-chka]

Please check my comment.
Once its done I'll merge you PR and it will be part of the next release (that should happen in 1-2 weeks, the time to have all the current PR approved & merged)

[mga-chka]

Hi, can you add a comment that it only works for non clustered redis? Even its "obivous" for a redis poweruser, it might prevent some false issues on the chproxy repo.

[DeanNeaht]

Fixed