propercasing take two (#1608)

Propercasing both request and response path for the ALPN pool

Risk Level: low (alpn-pool only)
Testing: n/a
Docs Changes: n/a
Release Notes: n/a
Fixes #1558

Signed-off-by: Alyssa Wilk <alyssar@chromium.org>
Signed-off-by: JP Simard <jp@jpsim.com>

mobile/envoy_build_config/extension_registry.h

@@ -8,6 +8,7 @@
 #include "source/extensions/filters/http/dynamic_forward_proxy/config.h"
 #include "source/extensions/filters/http/router/config.h"
 #include "source/extensions/filters/network/http_connection_manager/config.h"
+#include "source/extensions/http/header_formatters/preserve_case/preserve_case_formatter.h"
 #include "source/extensions/http/original_ip_detection/xff/config.h"
 #include "source/extensions/stat_sinks/metrics_service/config.h"
 #include "source/extensions/transport_sockets/raw_buffer/config.h"

mobile/library/common/config/config.cc

@@ -70,7 +70,12 @@ const std::string config_header = R"(
       "@type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
       auto_config:
         http2_protocol_options: {}
-        http_protocol_options: {}
+        http_protocol_options:
+          header_key_format:
+            stateful_formatter:
+              name: preserve_case
+              typed_config:
+                "@type": type.googleapis.com/envoy.extensions.http.header_formatters.preserve_case.v3.PreserveCaseFormatterConfig
 
 !ignore tls_socket_defs: &base_tls_socket
   name: envoy.transport_sockets.tls