docs(samples): added webhook code snippet (#401)

* Samples: added webhook code snippet

* added flask to requirments.txt

* changed res to string

* lint fix

* lint fix

* added space

* Revised code

* lint fix

* Added comment

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

samples/snippets/requirements.txt

@@ -1 +1,2 @@
 google-cloud-dialogflow==2.8.1
+Flask==2.0.1

samples/snippets/webhook.py

@@ -0,0 +1,37 @@
+# Copyright 2021, 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.
+
+# returns fullfillment response for dialogflow detect_intent call
+
+# [START dialogflow_webhook]
+def handleWebhook(request):
+
+    req = request.get_json()
+
+    responseText = ""
+    intent = req["queryResult"]["intent"]["displayName"]
+
+    if intent == "Default Welcome Intent":
+        responseText = "Hello from a GCF Webhook"
+    elif intent == "get-agent-name":
+        responseText = "My name is Flowhook"
+    else:
+        responseText = f"There are no fulfillment responses defined for Intent {intent}"
+
+    # You can also use the google.cloud.dialogflowcx_v3.types.WebhookRequest protos instead of manually writing the json object
+    res = {"fulfillmentMessages": [{"text": {"text": [responseText]}}]}
+
+    return res
+
+
+# [END dialogflow_webhook]

samples/snippets/webhook_test.py

@@ -0,0 +1,27 @@
+import flask
+import pytest
+
+from webhook import handleWebhook
+
+# Create a fake 'app' for generating test request contexts.
+
+request = {
+    "queryResult": {
+        "queryText": "hi",
+        "intent": {
+            "name": "projects/galstarter-316823/agent/intents/00c2877d-2440-447f-8dc1-045623a55bd4",
+            "displayName": "Default Welcome Intent",
+        },
+    }
+}
+
+
+@pytest.fixture(scope="module")
+def app():
+    return flask.Flask(__name__)
+
+
+def test_handleWebhook(app):
+    with app.test_request_context(json=request):
+        res = handleWebhook(flask.request)
+        assert "Hello from a GCF Webhook" in str(res)