feat(pubsub): implement GUAC for SubscriptionAdmin

[coryan]

Part of the work for #6463

---

This change is 

[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: dc04ccc92d51277a2751d8a9370a9903a500e3f7

• Public Access Build Logs
• Cloud Build Console (requires auth)
• Kokoro Logs (requires auth)

ℹ️ NOTE: Kokoro logs are linked from "Details" below.

[codecov]

Codecov Report

Merging #7432 (1222e6f) into main (1a2ddfb) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #7432      +/-   ##
==========================================
+ Coverage   93.61%   93.63%   +0.01%     
==========================================
  Files        1356     1359       +3     
  Lines      117762   118117     +355     
==========================================
+ Hits       110248   110602     +354     
- Misses       7514     7515       +1     

Impacted Files	Coverage Δ
google/cloud/pubsub/internal/subscriber_stub.h	100.00% <ø> (ø)
...ogle/cloud/internal/async_read_write_stream_impl.h	92.53% <100.00%> (+1.46%)	⬆️
...loud/internal/async_read_write_stream_impl_test.cc	96.96% <100.00%> (+0.34%)	⬆️
...ation_tests/subscription_admin_integration_test.cc	96.09% <100.00%> (+0.83%)	⬆️
google/cloud/pubsub/internal/subscriber_auth.cc	100.00% <100.00%> (ø)
google/cloud/pubsub/internal/subscriber_auth.h	100.00% <100.00%> (ø)
...ogle/cloud/pubsub/internal/subscriber_auth_test.cc	100.00% <100.00%> (ø)
google/cloud/pubsub/internal/subscriber_stub.cc	99.06% <100.00%> (+0.01%)	⬆️
...ogle/cloud/pubsub/subscription_admin_connection.cc	84.00% <100.00%> (+2.07%)	⬆️
google/cloud/bigtable/internal/common_client.h	94.02% <0.00%> (-5.98%)	⬇️
... and 6 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1a2ddfb...1222e6f. Read the comment docs.

[dbolduc]

Reviewed 11 of 11 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @coryan)

---

google/cloud/pubsub/subscription_admin_connection.cc, line 254 at r1 (raw file):

};

// Decorates a TopicAdminStub. This works for both mock and real stubs.

s/Topic/Subscription/

---

google/cloud/pubsub/subscription_admin_connection.cc, line 314 at r1 (raw file):

Quoted 9 lines of code…

  auto auth = [&] {
    if (opts.has<google::cloud::UnifiedCredentialsOption>()) {
      return google::cloud::internal::CreateAuthenticationStrategy(
          opts.get<google::cloud::UnifiedCredentialsOption>(), background->cq(),
          opts);
    }
    return google::cloud::internal::CreateAuthenticationStrategy(
        opts.get<google::cloud::GrpcCredentialOption>());
  }();

Note to selves: this logic appears in a lot of places. There is an opportunity to refactor.

---

google/cloud/pubsub/integration_tests/subscription_admin_integration_test.cc, line 216 at r1 (raw file):

Quoted 7 lines of code…

  if (UsingEmulator()) {
    options = Options{}
                  .set<UnifiedCredentialsOption>(MakeAccessTokenCredentials(
                      "test-only-invalid", std::chrono::system_clock::now() +
                                               std::chrono::minutes(15)))
                  .set<internal::UseInsecureChannelOption>(true);
  }

Does it make sense to move these emulator-only values into here?

google-cloud-cpp/google/cloud/pubsub/internal/defaults.cc

Lines 42 to 46 in 1a2ddfb

	auto emulator = internal::GetEnv("PUBSUB_EMULATOR_HOST");
	if (emulator.has_value()) {
	opts.set<EndpointOption>(*emulator).set<GrpcCredentialOption>(
	grpc::InsecureChannelCredentials());
	}

It seems weird that we default GrpcCredentialOption but not UnifiedCredentialsOption. (Maybe we shouldn't be setting either in defaults.cc)

[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: 179db952efcfdd8b0388b4ecb97deaff3aeea36b

• Public Access Build Logs
• Cloud Build Console (requires auth)
• Kokoro Logs (requires auth)

ℹ️ NOTE: Kokoro logs are linked from "Details" below.

[coryan]

Reviewable status: 10 of 11 files reviewed, 1 unresolved discussion (waiting on @dbolduc)

---

google/cloud/pubsub/subscription_admin_connection.cc, line 254 at r1 (raw file):

Previously, dbolduc (Darren Bolduc) wrote…

s/Topic/Subscription/

Fixed.

---

google/cloud/pubsub/subscription_admin_connection.cc, line 314 at r1 (raw file):

Previously, dbolduc (Darren Bolduc) wrote…

  auto auth = [&] {
    if (opts.has<google::cloud::UnifiedCredentialsOption>()) {
      return google::cloud::internal::CreateAuthenticationStrategy(
          opts.get<google::cloud::UnifiedCredentialsOption>(), background->cq(),
          opts);
    }
    return google::cloud::internal::CreateAuthenticationStrategy(
        opts.get<google::cloud::GrpcCredentialOption>());
  }();

Note to selves: this logic appears in a lot of places. There is an opportunity to refactor.

#7433

---

google/cloud/pubsub/integration_tests/subscription_admin_integration_test.cc, line 216 at r1 (raw file):

Previously, dbolduc (Darren Bolduc) wrote…

  if (UsingEmulator()) {
    options = Options{}
                  .set<UnifiedCredentialsOption>(MakeAccessTokenCredentials(
                      "test-only-invalid", std::chrono::system_clock::now() +
                                               std::chrono::minutes(15)))
                  .set<internal::UseInsecureChannelOption>(true);
  }

Does it make sense to move these emulator-only values into here?

google-cloud-cpp/google/cloud/pubsub/internal/defaults.cc

Lines 42 to 46 in 1a2ddfb

	auto emulator = internal::GetEnv("PUBSUB_EMULATOR_HOST");
	if (emulator.has_value()) {
	opts.set<EndpointOption>(*emulator).set<GrpcCredentialOption>(
	grpc::InsecureChannelCredentials());
	}

It seems weird that we default GrpcCredentialOption but not UnifiedCredentialsOption. (Maybe we shouldn't be setting either in defaults.cc)

We probably should switch to setting the unified credentials in this case. #7434

[dbolduc]

We probably should switch to setting the unified credentials in this case. #7434

Ah, yes. That makes more sense.

[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: 1222e6f2fcea9c17eacf5497ca7741b09d16757d

• Public Access Build Logs
• Cloud Build Console (requires auth)
• Kokoro Logs (requires auth)

ℹ️ NOTE: Kokoro logs are linked from "Details" below.