Added support for underscores in headers (#3057)

Calls with headers including underscores should no longer be rejected. 

Fix: added the
[--underscores_in_headers](https://cloud.google.com/endpoints/docs/openapi/specify-esp-v2-startup-options#security)
flag in both prod and test instance.

Closes #3055

deployment/terraform/modules/osv/osv_api.tf

@@ -126,7 +126,7 @@ resource "google_cloud_run_service" "api" {
         image = data.google_container_registry_image.api.image_url
         env {
           name  = "ESPv2_ARGS"
-          value = "^++^--transcoding_preserve_proto_field_names++--envoy_connection_buffer_limit_bytes=104857600"
+          value = "^++^--transcoding_preserve_proto_field_names++--envoy_connection_buffer_limit_bytes=104857600++--underscores_in_headers"
         }
         resources {
           limits = {

gcp/api/test_server.py

@@ -106,6 +106,7 @@ def start_esp(port, backend_port, credential_path, log_path):
         '--disable_tracing',
         '--service=api-test.osv.dev',
         '--rollout_strategy=managed',
+        '--underscores_in_headers',
         f'--listener_port={port}',
         f'--backend=grpc://{host}:{backend_port}',
         '--enable_debug',
@@ -134,6 +135,7 @@ def start_esp(port, backend_port, credential_path, log_path):
         '--disable_tracing',
         '--service=api-test.osv.dev',
         '--rollout_strategy=managed',
+        '--underscores_in_headers',
         f'--listener_port={port}',
         f'--backend=grpc://{host}:{backend_port}',
         f'--service_account_key=/esp/{credential_name}',