Example Airflow DAG that sends an email message through SendGrid (#7894)

* Example Airflow DAG that sends an email message through SendGrid

* Fix region tag format

* Fix Copyright header check

* Remove daily scheduling and unneeded task name

* Lint the sample

* Add unit test

* Fix imports in the unit test

* Update composer/workflows/email_operator_sendgrid_test.py

Co-authored-by: Leah E. Cole <6719667+leahecole@users.noreply.github.com>

composer/workflows/email_operator_sendgrid.py

@@ -0,0 +1,47 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+"""Example Airflow DAG that sends an email message through SendGrid.
+
+You must configure email notifications so that Airflow sends email through
+SendGrid. For more information, see
+https://cloud.google.com/composer/docs/composer-2/configure-email#sendgrid
+
+"""
+
+# [START composer_email_operator_sendgrid]
+
+import datetime
+
+import airflow
+from airflow.operators.email import EmailOperator
+
+
+with airflow.DAG(
+    "composer_sample_sendgrid",
+    start_date=datetime.datetime(2022, 1, 1),
+) as dag:
+
+    task_email = EmailOperator(
+        task_id="send-email",
+        conn_id="sendgrid_default",
+        # You can specify more than one recipient with a list.
+        to="user@example.com",
+        subject="EmailOperator test for SendGrid",
+        html_content="This is a test message sent through SendGrid.",
+        dag=dag,
+    )
+
+# [END composer_email_operator_sendgrid]

composer/workflows/email_operator_sendgrid_test.py

@@ -0,0 +1,26 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import internal_unit_testing
+
+
+def test_email_operator_sendgrid() -> None:
+    """Test that the DAG file can be successfully imported.
+    This tests that the DAG can be parsed, but does not run it in an Airflow
+    environment. This is a recommended confidence check by the official Airflow
+    docs: https://airflow.incubator.apache.org/tutorial.html#testing
+    """
+    from . import email_operator_sendgrid
+
+    internal_unit_testing.assert_has_valid_dag(email_operator_sendgrid)