Add Dropbox webhook integration.

This is just a basic Dropbox webhook integration. It just
notifies a user when something has changed, it does not
specify what changed. Doing so would require storing data,
as Dropbox API was created mainly for file managers, not
integrations like this.
Closes #5672

static/images/integrations/logos/dropbox.svg

@@ -0,0 +1 @@
+<svg id="Layer_1" data-name="Layer 1" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 235.45 200"><defs><style>.cls-1{fill:#0061ff;}</style></defs><title>DropboxGlyph</title><polygon class="cls-1" points="58.86 0 0 37.5 58.86 75 117.73 37.5 58.86 0"/><polygon class="cls-1" points="176.59 0 117.73 37.5 176.59 75 235.45 37.5 176.59 0"/><polygon class="cls-1" points="0 112.5 58.86 150 117.73 112.5 58.86 75 0 112.5"/><polygon class="cls-1" points="176.59 75 117.73 112.5 176.59 150 235.45 112.5 176.59 75"/><polygon class="cls-1" points="58.86 162.5 117.73 200 176.59 162.5 117.73 125 58.86 162.5"/></svg>

zerver/lib/integrations.py

@@ -284,6 +284,7 @@ WEBHOOK_INTEGRATIONS = [
         display_name='Desk.com',
         stream_name='desk'
     ),
+    WebhookIntegration('dropbox', ['productivity'], display_name='Dropbox'),
     WebhookIntegration('freshdesk', ['customer-support']),
     GithubIntegration(
         'github',

zerver/webhooks/dropbox/doc.md

@@ -0,0 +1,17 @@
+{!create-stream.md!}
+
+{!create-bot-construct-url.md!}
+
+{!append-topic.md!}
+
+Next, log into your account on [Dropbox](https://www.dropbox.com), go
+[there](https://www.dropbox.com/developers/apps) and click **Create app**.
+Follow the steps, and in **Webhooks** section add the webhook address you created above.
+Click **Add** button. The status of the webhook should say **Enabled**.
+In **Generated access token** section click **Generate** button.
+
+![](/static/images/integrations/dropbox/001.png)
+
+{!congrats.md!}
+
+![](/static/images/integrations/dropbox/002.png)

zerver/webhooks/dropbox/fixtures/file_updated.json

@@ -0,0 +1,12 @@
+{
+    "list_folder": {
+        "accounts": [
+            "dbid:AAH4f99T0taONIb-OurWxbNQ6ywGRopQngc"
+        ]
+    },
+    "delta": {
+        "users": [
+            12345678
+        ]
+    }
+}

zerver/webhooks/dropbox/tests.py

@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+from typing import Text
+
+from zerver.lib.test_classes import WebhookTestCase
+
+class DropboxHookTests(WebhookTestCase):
+    STREAM_NAME = 'test'
+    URL_TEMPLATE = "/api/v1/external/dropbox?&api_key={api_key}"
+    FIXTURE_DIR_NAME = 'dropbox'
+
+    def test_file_updated(self) -> None:
+        expected_subject = u"Dropbox"
+        expected_message = u"File has been updated on Dropbox!"
+
+        self.send_and_test_stream_message('file_updated', expected_subject, expected_message,
+                                          content_type="application/x-www-form-urlencoded")
+
+    def get_body(self, fixture_name: Text) -> Text:
+        return self.fixture_data("dropbox", fixture_name, file_type="json")
+
+    def test_verification_request(self) -> None:
+        self.subscribe(self.test_user, self.STREAM_NAME)
+        get_params = {'stream_name': self.STREAM_NAME,
+                      'challenge': '9B2SVL4orbt5DxLMqJHI6pOTipTqingt2YFMIO0g06E',
+                      'api_key': self.test_user.api_key}
+        result = self.client_get(self.url, get_params)
+
+        self.assert_in_response('9B2SVL4orbt5DxLMqJHI6pOTipTqingt2YFMIO0g06E', result)

zerver/webhooks/dropbox/view.py

@@ -0,0 +1,18 @@
+from typing import Text
+from django.http import HttpRequest, HttpResponse
+from zerver.lib.actions import check_send_stream_message
+from zerver.lib.response import json_success
+from zerver.decorator import REQ, has_request_variables, api_key_only_webhook_view
+from zerver.models import UserProfile
+
+@api_key_only_webhook_view('Dropbox')
+@has_request_variables
+def api_dropbox_webhook(request: HttpRequest, user_profile: UserProfile,
+                        stream: Text=REQ(default='test'),
+                        topic: Text=REQ(default='Dropbox')) -> HttpResponse:
+    if request.method == 'GET':
+        return HttpResponse(request.GET['challenge'])
+    elif request.method == 'POST':
+        check_send_stream_message(user_profile, request.client,
+                                  stream, topic, "File has been updated on Dropbox!")
+        return json_success()