support envoy headers_to_add for AuthService objects

[travisghansen]

Please describe your use case / problem.
I would like to be able to inject headers that can be consumed by the auth service but not sent by the client.

Describe the solution you'd like
Envoy supports a headers_to_add parameter that seems to be missing or not mapped by ambassador. Note that this is separate from the allowed_headers option that appears to coincide with the AuthService option allowed_request_headers.

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

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[travisghansen]

Still valid.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[travisghansen]

Yeah, still valid.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[travisghansen]

Valid.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[travisghansen]

sigh..

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[travisghansen]

Ugh.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[travisghansen]

Ugh.

[kflynn]

Huh, my apologies for losing this bug! Community member @jasonewang actually added the add_auth_headers element to the AuthService for 1.6.0; does that do what you need?

Thanks! and sorry, again, for not updating this issue when that feature went in.

[travisghansen]

Does it map to the headers_to_add attribute? If so we should be good.

[kflynn]

Yup, it does. 🙂 I'll go ahead and close this -- if it doesn't work out for you, please reopen!