AWS request signing filter virtual host-specific config

*Title*: *AWS request signing filter virtual host-specific config*

*Description*:

I have Envoy deployed with a single TLS listener that is using virtual hosts. I need to tell each virtual host to use the `typed_per_filter_config` to apply the `envoy.filters.http.aws_request_signing` filter. However, when I apply the filter on the virtual host level, the following error is displayed:

```
The filter envoy.filters.http.aws_request_signing doesn’t support virtual host-specific configurations
```

Is there a technical reason this filter cannot be applied to a virtual host config? Technical being either the extension does not implement the correct interface and it just needs to be updated or a deeper technical issue that would cause issues when applied at the virtual host level?

When looking at the [AWS Lambda filter](https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/aws_lambda_filter.html), it states it explicitly supports per-filter configuration. I'm assuming that means it could apply at the route/virtual host level?

Also, I looked in the documentation but could not find it… Is there a way to get a list of extensions that are available per-filter config level?

*Relevant Links*:

- [AWS Request Signing Filter](https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/aws_request_signing_filter)
- [AWS Request Signing Filter Source Code](https://github.com/envoyproxy/envoy/tree/main/source/extensions/filters/http/aws_request_signing)