Transparent proxy, subdomain buckets and auth fixes

[janosch-strato]

This pull request adds several new features, described in their respective commits.

I based it on the code from https://github.com/clyso/chorus/pull/79 but can easily rebase as required.

I am happy to make adaptions.

[arttor]

@janosch-strato thank you for your contribution and sorry for the delayed response.

your PR is quite large and based on commit messages, it contains multiple features. so in current state it will be hard to review. can you please do following:

• move out virtual domain support to a separate PR
• move out s3 signature bugfixes to a separate PR. please also add bug description in PR description or create an issue
• move out config refactoring and other refactoring to a separate PR. I can say that we might reject config refactoring change because there is ongoing work to support openstack swift api and it contains conflicting config changes

[janosch-strato]

@arttor thank you for taking a look at the pull request.

I can reorder and split my changes of course. As they are partly based on the pull request of @doomguy-stg I'll put this one on hold until that pull request is resolved / closed so that we have common ground what the code should be based on. I'll monitor the progress and come back to this one soon after.