Merge branch 'shemgyll-unitialized-repositories' into 'master'

Documentation: Add "Unitialized repositories" section to Integrations

See merge request gitlab-org/gitlab!29933

doc/user/project/integrations/overview.md

@@ -47,7 +47,7 @@ Click on the service links to see further configuration instructions and details
 | [Microsoft teams](microsoft_teams.md) |  Receive notifications for actions that happen on GitLab into a room on Microsoft Teams using Office 365 Connectors | No |
 | Packagist | Update your project on Packagist, the main Composer repository | Yes |
 | Pipelines emails | Email the pipeline status to a list of recipients | No |
-| [Slack Notifications](slack.md) | Send GitLab events (e.g. issue created) to Slack as notifications | No |
+| [Slack Notifications](slack.md) | Send GitLab events (for example, an issue was created) to Slack as notifications | No |
 | [Slack slash commands](slack_slash_commands.md) **(CORE ONLY)** | Use slash commands in Slack to control GitLab | No |
 | [GitLab Slack application](gitlab_slack_application.md) **(FREE ONLY)** | Use Slack's official application | No |
 | PivotalTracker | Project Management Software (Source Commits Endpoint) | No |
@@ -93,6 +93,15 @@ From this page, you can repeat delivery with the same data by clicking **Resend
 
 ![Recent deliveries](img/webhook_logs.png)
 
+### Uninitialized repositories
+
+Some integrations fail with an error `Test Failed. Save Anyway` when you attempt to set them up on
+uninitialized repositories. This is because the default service test uses push data to build the
+payload for the test request, and it fails, because there are no push events for the project.
+
+To resolve this error, initialize the repository by pushing a test file to the project and set up
+the integration again.
+
 ## Contributing to integrations
 
 Because GitLab is open source we can ship with the code and tests for all