[mod_proxy] SilentOnStatus to complement FailOnStatus

[Nestor Urquiza <ne...@gmail.com>]

Hello,

I am wondering if the below makes sense as a user story that could be
implemented:

As a user of mod-proxy
I want to silently retry a request when certain status code is returned
from the backend
So that the client experience goes from receiving an instant error to
waiting longer for a response

This will allow restarting backend servers without communicating to the
user system errors. The user for sure would prefer to see a delay in a
response than a system error which basically invites them to manually retry
again within seconds.

This also creates opportunities for more agile and less disruptive backend
deployments. It is OK to wait a bit for a response from time to time. It is
never right to get an error for a transient action like a server restart.

If you agree I will proceed to create a "feature request" in the tracking
system.

Best,
- Nestor