In https://gitlab.com/gitlab-org/gitlab/-/merge_requests/40694, we made
some changes to the Workhorse direct upload API to support custom
domains in Azure.

While this worked, it made it quite complicated for Workhorse to handle
since the Go Cloud library (https://gocloud.dev/howto/blob/) expects all
the object store information to be available in a single URL.

To simplify this, we added a custom storage domain as a `domain` query
parameter in
https://gitlab.com/gitlab-org/gitlab-workhorse/-/merge_requests/593.