test: add support for channel configurators to session client (#2880)

Change-Id: Iff9040f0ed03754f2424ffafb143752f69e0d8a6

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Fixes #<issue_number_goes_here> ☕️

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https://togithub.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md).

Author: igorbernstein2

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/internal/compat/GaxBasicChannelProvider.java

@@ -15,6 +15,7 @@
  */
 package com.google.cloud.bigtable.data.v2.internal.compat;
 
+import com.google.api.core.ApiFunction;
 import com.google.api.gax.grpc.InstantiatingGrpcChannelProvider;
 import com.google.auth.Credentials;
 import com.google.bigtable.v2.FeatureFlags;
@@ -32,11 +33,15 @@
 import javax.annotation.Nullable;
 
 public class GaxBasicChannelProvider implements ChannelProvider {
+  private final ApiFunction<ManagedChannelBuilder, ManagedChannelBuilder> channelConfigurator;
   private final InstantiatingGrpcChannelProvider inner;
   private final @Nullable CallCredentials credentials;
 
+  @SuppressWarnings("rawtypes")
   public GaxBasicChannelProvider(
       InstantiatingGrpcChannelProvider inner, @Nullable Credentials credentials) {
+    this.channelConfigurator =
+        Optional.ofNullable(inner.toBuilder().getChannelConfigurator()).orElse(b -> b);
     this.inner = inner.toBuilder().setAttemptDirectPath(false).build();
     this.credentials = Optional.ofNullable(credentials).map(MoreCallCredentials::from).orElse(null);
   }
@@ -56,6 +61,7 @@ public ManagedChannelBuilder<?> newChannelBuilder() {
       if (credentials != null) {
         builder.intercept(new CredInterceptor(credentials));
       }
+      builder = channelConfigurator.apply(builder);
       return builder;
     } catch (IOException e) {
       throw new RuntimeException("Gax channel provider failed to provide a channel builder", e);

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/internal/compat/GaxDirectAccessChannelProvider.java

@@ -15,6 +15,7 @@
  */
 package com.google.cloud.bigtable.data.v2.internal.compat;
 
+import com.google.api.core.ApiFunction;
 import com.google.api.gax.grpc.InstantiatingGrpcChannelProvider;
 import com.google.auth.Credentials;
 import com.google.bigtable.v2.FeatureFlags;
@@ -26,6 +27,10 @@
 
 public class GaxDirectAccessChannelProvider implements ChannelProvider {
   private final InstantiatingGrpcChannelProvider inner;
+
+  @SuppressWarnings("rawtypes")
+  private final ApiFunction<ManagedChannelBuilder, ManagedChannelBuilder> channelConfigurator;
+
   private final Optional<ChannelProvider> fallback;
 
   public static ChannelProvider create(
@@ -67,6 +72,9 @@ private GaxDirectAccessChannelProvider(
       @SuppressWarnings("unused") @Nullable Credentials credentials,
       Optional<ChannelProvider> fallback) {
     this.inner = directAccessProvider;
+    this.channelConfigurator =
+        Optional.ofNullable(directAccessProvider.toBuilder().getChannelConfigurator())
+            .orElse(b -> b);
     this.fallback = fallback;
   }
 
@@ -81,7 +89,7 @@ public FeatureFlags updateFeatureFlags(FeatureFlags featureFlags) {
   @Override
   public ManagedChannelBuilder<?> newChannelBuilder() {
     try {
-      return inner.createChannelBuilder();
+      return channelConfigurator.apply(inner.createChannelBuilder());
     } catch (IOException e) {
       throw new RuntimeException("Gax channel provider failed to provide a channel builder", e);
     }