Add shard information to sentry
As sidekiq shards are migrated to to K8s it would be helpful to filter Sentry exceptions by shard. Now that we are able to inject extra env variables it should be possible to use an env variable like GITLAB_SENTRY_EXTRA_CONTEXT
suggested in gitlab-com/gl-infra/production#2285 (comment 362787698)
Edited by John Jarvis