Support setting "status_on_error" and "failure_mode_allow" for auth service config

[TonkWorks]

Please describe your use case / problem.
When an external authservice fails to respond in time - a 403 is returned.

Envoy 1.10 now supports customizing the status code that is returned.
So for example a 503 can be returned and the auth service can be retried.

https://www.envoyproxy.io/docs/envoy/latest/api-v2/config/filter/http/ext_authz/v2/ext_authz.proto

envoy issue ticket: envoyproxy/envoy#6119

Describe the solution you'd like
Support for setting AuthService config for:
status_on_error and failure_mode_allow

https://www.envoyproxy.io/docs/envoy/latest/api-v2/config/filter/http/ext_authz/v2/ext_authz.proto

Describe alternatives you've considered
N/A

Additional context
N/A

[TonkWorks]

nvm this looks like this won't be supported until envoy 1.11

[justinfiore]

@TonkWorks It looks like the code needed for your commit is included in the version of the DataWire Envoy Fork that the latest version of Ambassador just released with https://blog.getambassador.io/ambassador-0-72-ddaca31c75f8
which is commit: datawire/envoy@8f57f7d

So is it now safe to create a PR with your changes and get them into the next Ambassador release?
or is there another reason to wait for Envoy 1.11?

[TonkWorks]

You are right - tested and works with latest master. I'll make a PR
PR - #1632

[justinfiore]

Thanks @TonkWorks for getting that PR in!