Add documentation for Hangouts Chat integration

changelogs/unreleased/hangouts_chat_integration.yml

+---
+title: Add Hangouts Chat integration
+merge_request:
+author: Kukovskii Vladimir
+type: added

doc/api/services.md

@@ -443,6 +443,52 @@ Get Gemnasium service settings for a project.
 GET /projects/:id/services/gemnasium
 ```
 
+## Hangouts Chat
+
+Google GSuite team collaboration tool.
+
+### Create/Edit Hangouts Chat service
+
+Set Hangouts Chat service for a project.
+
+```
+PUT /projects/:id/services/hangouts_chat
+```
+
+>**Note:** Specific event parameters (e.g. `push_events` flag) were [introduced in v10.4][11435]
+
+Parameters:
+
+| Parameter | Type | Required | Description |
+| --------- | ---- | -------- | ----------- |
+| `webhook` | string | true | The Hangouts Chat webhook. e.g. https://chat.googleapis.com/v1/spaces... |
+| `notify_only_broken_pipelines` | boolean | false | Send notifications for broken pipelines |
+| `notify_only_default_branch` | boolean | false | Send notifications only for the default branch |
+| `push_events` | boolean | false | Enable notifications for push events |
+| `issues_events` | boolean | false | Enable notifications for issue events |
+| `confidential_issues_events` | boolean | false | Enable notifications for confidential issue events |
+| `merge_requests_events` | boolean | false | Enable notifications for merge request events |
+| `tag_push_events` | boolean | false | Enable notifications for tag push events |
+| `note_events` | boolean | false | Enable notifications for note events |
+| `pipeline_events` | boolean | false | Enable notifications for pipeline events |
+| `wiki_page_events` | boolean | false | Enable notifications for wiki page events |
+
+### Delete Hangouts Chat service
+
+Delete Hangouts Chat service for a project.
+
+```
+DELETE /projects/:id/services/hangouts_chat
+```
+
+### Get Hangouts Chat service settings
+
+Get Hangouts Chat service settings for a project.
+
+```
+GET /projects/:id/services/hangouts_chat
+```
+
 ## HipChat
 
 Private group chat and IM

doc/user/project/integrations/hangouts_chat.md

+# Hangouts Chat service
+
+The Hangouts Chat service sends notifications from GitLab to the room for which the webhook was created.
+
+## On Hangouts Chat
+
+1. Open the chat room in which you want to see the notifications.
+1. From the chat room menu, select **Configure Webhooks**.
+1. Click on **ADD WEBHOOK** and fill in the name of the bot that will post the messages. Optionally define avatar.
+1. Click **SAVE** and copy the **Webhook URL** of your webhook.
+
+Details: https://developers.google.com/hangouts/chat/how-tos/webhooks
+
+## On GitLab
+
+When you have **Webhook URL** for your Hangouts Chat room webhook, you can setup the GitLab service.
+
+1. Navigate to the [Integrations page](project_services.md#accessing-the-project-services) in your project's settings, i.e. **Project > Settings > Integrations**.
+1. Select the **Hangouts Chat** project service to configure it.
+1. Check the **Active** checkbox to turn on the service.
+1. Check the checkboxes corresponding to the GitLab events you want to receive.
+1. Paste the **Webhook URL** that you copied from the Hangouts Chat configuration step.
+1. Configure the remaining options and click `Save changes`.
+
+Your Hangouts Chat room will now start receiving GitLab event notifications as configured.
+
+![Hangouts Chat configuration](img/hangouts_chat_configuration.png)

doc/user/project/integrations/project_services.md

@@ -35,6 +35,7 @@ Click on the service links to see further configuration instructions and details
 | External Wiki | Replaces the link to the internal wiki with a link to an external wiki |
 | Flowdock | Flowdock is a collaboration web app for technical teams |
 | Gemnasium   _(Has been deprecated in GitLab 11.0)_ | Gemnasium monitors your project dependencies and alerts you about updates and security vulnerabilities |
+| [Hangouts Chat](hangouts_chat.md) | Receive events notifications in Google Hangouts Chat |
 | [HipChat](hipchat.md) | Private group chat and IM |
 | [Irker (IRC gateway)](irker.md) | Send IRC messages, on update, to a list of recipients through an Irker gateway |
 | [JIRA](jira.md) | JIRA issue tracker |