management: Support sending custom headers when testing a webhook.

this commit adds an option to specify custom headers when using the
`./manage.py send_webhook_fixture_message` tool.

templates/zerver/api/incoming-webhooks-walkthrough.md

@@ -217,6 +217,16 @@ Using either method will create a message in Zulip:
 
 <img class="screenshot" src="/static/images/api/helloworld-webhook.png" />
 
+Some webhooks require custom HTTP headers, which can be passed using
+`./manage.py send_webhook_fixture_message --custom-headers`.  For
+example:
+
+    --custom-headers='{"X-Custom-Header": "value"}'
+
+The format is a JSON dictionary, so make sure that the header names do
+not contain any spaces in them and that you use the precise quoting
+approach shown above.
+
 ## Step 4: Create tests
 
 Every webhook integration should have a corresponding test file:

zerver/management/commands/send_webhook_fixture_message.py

@@ -1,7 +1,7 @@
-
 import os
-
 import ujson
+from typing import Union, Dict
+
 from django.conf import settings
 from django.core.management.base import CommandParser
 from django.test import Client
@@ -18,6 +18,14 @@ Example:
     --fixture=zerver/webhooks/integration/fixtures/name.json \
     '--url=/api/v1/external/integration?stream=stream_name&api_key=api_key'
 
+To pass custom headers along with the webhook message use the --custom-headers
+command line option.
+Example:
+    --custom-headers='{"X-Custom-Header": "value"}'
+
+The format is a JSON dictionary, so make sure that the header names do
+not contain any spaces in them and that you use the precise quoting
+approach shown above.
 """
 
     def add_arguments(self, parser: CommandParser) -> None:
@@ -33,8 +41,30 @@ Example:
                             help='The url on your Zulip server that you want '
                                  'to post the fixture to')
 
+        parser.add_argument('-H', '--custom-headers',
+                            dest='custom-headers',
+                            type=str,
+                            help='The headers you want to provide along with '
+                                 'your mock request to Zulip.')
+
         self.add_realm_args(parser, help="Specify which realm/subdomain to connect to; default is zulip")
 
+    def parse_headers(self, custom_headers: Union[None, str]) -> Union[None, Dict[str, str]]:
+        headers = {}
+        if not custom_headers:
+            return None
+        try:
+            custom_headers_dict = ujson.loads(custom_headers)
+            for header in custom_headers_dict:
+                if len(header.split(" ")) > 1:
+                    raise ValueError("custom header '%s' contains a space." % (header))
+                headers["HTTP_" + header.upper().replace("-", "_")] = str(custom_headers_dict[header])
+            return headers
+        except ValueError as ve:
+            print('Encountered an error while attempting to parse custom headers: %s' % (ve))
+            print('Note: all strings must be enclosed within "" instead of \'\'')
+            exit(1)
+
     def handle(self, **options: str) -> None:
         if options['fixture'] is None or options['url'] is None:
             self.print_help('./manage.py', 'send_webhook_fixture_message')
@@ -46,14 +76,19 @@ Example:
             print('Fixture {} does not exist'.format(options['fixture']))
             exit(1)
 
+        headers = self.parse_headers(options['custom-headers'])
         json = self._get_fixture_as_json(full_fixture_path)
         realm = self.get_realm(options)
         if realm is None:
             realm = get_realm("zulip")
 
         client = Client()
-        result = client.post(options['url'], json, content_type="application/json",
-                             HTTP_HOST=realm.host)
+        if headers:
+            result = client.post(options['url'], json, content_type="application/json",
+                                 HTTP_HOST=realm.host, **headers)
+        else:
+            result = client.post(options['url'], json, content_type="application/json",
+                                 HTTP_HOST=realm.host)
         if result.status_code != 200:
             print('Error status %s: %s' % (result.status_code, result.content))
             exit(1)

zerver/tests/test_management_commands.py

@@ -18,6 +18,7 @@ from zerver.lib.test_helpers import stdout_suppressed
 from zerver.lib.test_runner import slow
 from zerver.models import Recipient, get_user_profile_by_email, get_stream
 
+from zerver.management.commands.send_webhook_fixture_message import Command
 from zerver.lib.test_helpers import most_recent_message
 from zerver.models import get_realm, UserProfile, Realm
 from confirmation.models import RealmCreationKey, generate_realm_creation_url
@@ -213,6 +214,29 @@ class TestSendWebhookFixtureMessage(TestCase):
         client.post.assert_called_once_with(self.url, {}, content_type="application/json",
                                             HTTP_HOST="zulip.testserver")
 
+    @patch('zerver.management.commands.send_webhook_fixture_message.Command._get_fixture_as_json')
+    @patch('zerver.management.commands.send_webhook_fixture_message.Command._does_fixture_path_exist')
+    @patch('zerver.management.commands.send_webhook_fixture_message.Command.parse_headers')
+    def test_check_post_request_with_improper_custom_header(self,
+                                                            parse_headers_mock: MagicMock,
+                                                            does_fixture_path_exist_mock: MagicMock,
+                                                            get_fixture_as_json_mock: MagicMock) -> None:
+        does_fixture_path_exist_mock.return_value = True
+        get_fixture_as_json_mock.return_value = "{}"
+
+        improper_headers = '{"X-Custom - Headers": "some_val"}'
+        with self.assertRaises(SystemExit) as se:
+            call_command(self.COMMAND_NAME, fixture=self.fixture_path, url=self.url, custom_headers=improper_headers)
+
+        parse_headers_mock.assert_called_once_with(improper_headers)
+
+    def test_parse_headers_method(self) -> None:
+        command = Command()
+        self.assertEqual(command.parse_headers(None), None)
+        self.assertEqual(command.parse_headers('{"X-Custom-Header": "value"}'), {"HTTP_X_CUSTOM_HEADER": "value"})
+        with self.assertRaises(SystemExit):
+            command.parse_headers('{"X-Custom - Headers": "some_val"}')
+
 class TestGenerateRealmCreationLink(ZulipTestCase):
     COMMAND_NAME = "generate_realm_creation_link"