We run mutliple instances of anubis behind a load balancer. Each of
these generates its own secret key to check proof of work from clients.
This means that if you get rebalanced to a new backend you need to
recalculate the proof of work challenge. This can get annoying during
Gitea upgrades (or just general restarts).
Make this less annoying by optionally setting a consistent secret key
across all of the backends.
This is optional to make deployment and rollback easy.
Change-Id: If4d8c34145e7af994fcf033133d6efac436cb27e
Clark Boylan
e0c35625dd