feat: allow quota project to be passed to create_channel (#58)

* feat: allow quota project to be passed to create_channel

* chore: update test name

* chore: lint and increase auth lib version

* chore: fix lint

* Update setup.py
diff --git a/google/api_core/grpc_helpers.py b/google/api_core/grpc_helpers.py
index 2203968..dfc8442 100644
--- a/google/api_core/grpc_helpers.py
+++ b/google/api_core/grpc_helpers.py
@@ -176,7 +176,12 @@
         return _wrap_unary_errors(callable_)
 
 
-def _create_composite_credentials(credentials=None, credentials_file=None, scopes=None, ssl_credentials=None):
+def _create_composite_credentials(
+        credentials=None,
+        credentials_file=None,
+        scopes=None,
+        ssl_credentials=None,
+        quota_project_id=None):
     """Create the composite credentials for secure channels.
 
     Args:
@@ -191,6 +196,7 @@
             are passed to :func:`google.auth.default`.
         ssl_credentials (grpc.ChannelCredentials): Optional SSL channel
             credentials. This can be used to specify different certificates.
+        quota_project_id (str): An optional project to use for billing and quota.
 
     Returns:
         grpc.ChannelCredentials: The composed channel credentials object.
@@ -210,6 +216,9 @@
     else:
         credentials, _ = google.auth.default(scopes=scopes)
 
+    if quota_project_id:
+        credentials = credentials.with_quota_project(quota_project_id)
+
     request = google.auth.transport.requests.Request()
 
     # Create the metadata plugin for inserting the authorization header.
@@ -229,7 +238,14 @@
     )
 
 
-def create_channel(target, credentials=None, scopes=None, ssl_credentials=None, credentials_file=None, **kwargs):
+def create_channel(
+        target,
+        credentials=None,
+        scopes=None,
+        ssl_credentials=None,
+        credentials_file=None,
+        quota_project_id=None,
+        **kwargs):
     """Create a secure channel with credentials.
 
     Args:
@@ -245,6 +261,7 @@
         credentials_file (str): A file with credentials that can be loaded with
             :func:`google.auth.load_credentials_from_file`. This argument is
             mutually exclusive with credentials.
+        quota_project_id (str): An optional project to use for billing and quota.
         kwargs: Additional key-word args passed to
             :func:`grpc_gcp.secure_channel` or :func:`grpc.secure_channel`.
 
@@ -259,7 +276,8 @@
         credentials=credentials,
         credentials_file=credentials_file,
         scopes=scopes,
-        ssl_credentials=ssl_credentials
+        ssl_credentials=ssl_credentials,
+        quota_project_id=quota_project_id,
     )
 
     if HAS_GRPC_GCP:
diff --git a/google/api_core/grpc_helpers_async.py b/google/api_core/grpc_helpers_async.py
index 1dfe8b9..9a994e9 100644
--- a/google/api_core/grpc_helpers_async.py
+++ b/google/api_core/grpc_helpers_async.py
@@ -206,7 +206,14 @@
         return _wrap_stream_errors(callable_)
 
 
-def create_channel(target, credentials=None, scopes=None, ssl_credentials=None, credentials_file=None, **kwargs):
+def create_channel(
+        target,
+        credentials=None,
+        scopes=None,
+        ssl_credentials=None,
+        credentials_file=None,
+        quota_project_id=None,
+        **kwargs):
     """Create an AsyncIO secure channel with credentials.
 
     Args:
@@ -222,6 +229,7 @@
         credentials_file (str): A file with credentials that can be loaded with
             :func:`google.auth.load_credentials_from_file`. This argument is
             mutually exclusive with credentials.
+        quota_project_id (str): An optional project to use for billing and quota.
         kwargs: Additional key-word args passed to :func:`aio.secure_channel`.
 
     Returns:
@@ -235,7 +243,8 @@
         credentials=credentials,
         credentials_file=credentials_file,
         scopes=scopes,
-        ssl_credentials=ssl_credentials
+        ssl_credentials=ssl_credentials,
+        quota_project_id=quota_project_id,
     )
 
     return aio.secure_channel(target, composite_credentials, **kwargs)
diff --git a/setup.py b/setup.py
index efa4a12..6e82e54 100644
--- a/setup.py
+++ b/setup.py
@@ -31,7 +31,7 @@
 dependencies = [
     "googleapis-common-protos >= 1.6.0, < 2.0dev",
     "protobuf >= 3.12.0",
-    "google-auth >= 1.18.0, < 2.0dev",
+    "google-auth >= 1.19.1, < 2.0dev",
     "requests >= 2.18.0, < 3.0.0dev",
     "setuptools >= 34.0.0",
     "six >= 1.10.0",
diff --git a/tests/asyncio/test_grpc_helpers_async.py b/tests/asyncio/test_grpc_helpers_async.py
index d56c4c6..924a74c 100644
--- a/tests/asyncio/test_grpc_helpers_async.py
+++ b/tests/asyncio/test_grpc_helpers_async.py
@@ -365,6 +365,23 @@
 
 @mock.patch("grpc.composite_channel_credentials")
 @mock.patch("grpc.experimental.aio.secure_channel")
+def test_create_channel_explicit_with_quota_project(grpc_secure_channel, composite_creds_call):
+    target = "example.com:443"
+    composite_creds = composite_creds_call.return_value
+
+    credentials = mock.create_autospec(google.auth.credentials.Credentials, instance=True)
+
+    channel = grpc_helpers_async.create_channel(
+        target, credentials=credentials, quota_project_id="project-foo"
+    )
+
+    credentials.with_quota_project.assert_called_once_with("project-foo")
+    assert channel is grpc_secure_channel.return_value
+    grpc_secure_channel.assert_called_once_with(target, composite_creds)
+
+
+@mock.patch("grpc.composite_channel_credentials")
+@mock.patch("grpc.experimental.aio.secure_channel")
 @mock.patch(
     "google.auth.load_credentials_from_file",
     return_value=(mock.sentinel.credentials, mock.sentinel.project)
diff --git a/tests/unit/test_grpc_helpers.py b/tests/unit/test_grpc_helpers.py
index e2f3666..f8fed40 100644
--- a/tests/unit/test_grpc_helpers.py
+++ b/tests/unit/test_grpc_helpers.py
@@ -337,6 +337,29 @@
 
 @mock.patch("grpc.composite_channel_credentials")
 @mock.patch("grpc.secure_channel")
+def test_create_channel_explicit_with_quota_project(grpc_secure_channel, composite_creds_call):
+    target = "example.com:443"
+    composite_creds = composite_creds_call.return_value
+
+    credentials = mock.create_autospec(google.auth.credentials.Credentials, instance=True)
+
+    channel = grpc_helpers.create_channel(
+        target,
+        credentials=credentials,
+        quota_project_id="project-foo"
+    )
+
+    credentials.with_quota_project.assert_called_once_with("project-foo")
+
+    assert channel is grpc_secure_channel.return_value
+    if grpc_helpers.HAS_GRPC_GCP:
+        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
+    else:
+        grpc_secure_channel.assert_called_once_with(target, composite_creds)
+
+
+@mock.patch("grpc.composite_channel_credentials")
+@mock.patch("grpc.secure_channel")
 @mock.patch(
     "google.auth.load_credentials_from_file",
     return_value=(mock.sentinel.credentials, mock.sentinel.project)