cache per user

[mga-chka]

Description

cf #256, having the same cache for all users could be a security leak with wildcarded user (and is a smaller leak without wildcarded user).
The aim is to have a cache per user by default and let the admin choses whether or not the cache should be shared btw all users

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
  after the upgrade, all the queries put in cache (redis or filesystem) put by a previous version of chproxy will not be seen by the new version. Moreover, by default the queries won't be shared per user unless explicitly asked in the conf.

Further comments

[render]

Your Render PR Server URL is https://chproxy-pr-258.onrender.com.

Follow its progress at https://dashboard.render.com/static/srv-cdh79dsgqg4dhlo57ilg.

[sigua-cs]

LGTM