feat: better support for PSC and VPC-SC (#8453)

When using [PSC] (Private Service Connect) or [VPC-SC] (Virtual Private
Cloud - Service Controls) we need to specify the `authority` in each
gRPC request. This is the HTTP/2 analog of a `Host` header, and allows
applications to access a service while using a custom endpoint. For
example, the target endpoint could be `pubsub-custom.p.googleapis.com`,
but the authority field remains `pubsub.googleapis.com`.

[PSC]: https://cloud.google.com/vpc/docs/private-service-connect
[VPC-SC]: https://cloud.google.com/vpc-service-controls

Author: coryan

generator/integration_tests/golden/internal/golden_kitchen_sink_metadata_decorator.cc

@@ -121,6 +121,9 @@ void GoldenKitchenSinkMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata(
         "x-goog-user-project", options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

generator/integration_tests/golden/internal/golden_thing_admin_metadata_decorator.cc

@@ -230,6 +230,9 @@ void GoldenThingAdminMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata(
         "x-goog-user-project", options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

generator/internal/metadata_decorator_generator.cc

@@ -348,6 +348,9 @@ void $metadata_class_name$::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata(
         "x-goog-user-project", options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 )""");
 

google/cloud/accessapproval/internal/access_approval_metadata_decorator.cc

@@ -109,6 +109,9 @@ void AccessApprovalMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata("x-goog-user-project",
                         options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/accesscontextmanager/internal/access_context_manager_metadata_decorator.cc

@@ -292,6 +292,9 @@ void AccessContextManagerMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata("x-goog-user-project",
                         options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/apigateway/internal/api_gateway_metadata_decorator.cc

@@ -192,6 +192,9 @@ void ApiGatewayServiceMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata("x-goog-user-project",
                         options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/apigeeconnect/internal/connection_metadata_decorator.cc

@@ -55,6 +55,9 @@ void ConnectionServiceMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata("x-goog-user-project",
                         options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/appengine/internal/applications_metadata_decorator.cc

@@ -99,6 +99,9 @@ void ApplicationsMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata("x-goog-user-project",
                         options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/appengine/internal/authorized_certificates_metadata_decorator.cc

@@ -86,6 +86,9 @@ void AuthorizedCertificatesMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata("x-goog-user-project",
                         options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/appengine/internal/authorized_domains_metadata_decorator.cc

@@ -55,6 +55,9 @@ void AuthorizedDomainsMetadata::SetMetadata(grpc::ClientContext& context) {
     context.AddMetadata("x-goog-user-project",
                         options.get<UserProjectOption>());
   }
+  if (options.has<AuthorityOption>()) {
+    context.set_authority(options.get<AuthorityOption>());
+  }
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END