Artifacts metadata field will be used to store a filename of gzipped
file containing metadata definition for given artifacts archive.

InfluxDB over UDP doesn't use authentication, thus there's no need for
these settings.

This removes the need for Sidekiq and any overhead/problems introduced
by TCP. There are a few things to take into account:

1. When writing data to InfluxDB you may still get an error if the
   server becomes unavailable during the write. Because of this we're
   catching all exceptions and just ignore them (for now).
2. Writing via UDP apparently requires the timestamp to be in
   nanoseconds. Without this data either isn't written properly.
3. Due to the restrictions on UDP buffer sizes we're writing metrics one
   by one, instead of writing all of them at once.

- Offloads uploading to GitLab Workhorse
- Use /authorize request for fast uploading
- Added backup recipes for artifacts
- Support download acceleration using X-Sendfile

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This column is queried when creating a new project, without an index
this query would lead to a sequence scan.