<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Work on this issue](https://contributors.gitlab.com/manage-issue?action=work&projectId=278964&issueIid=392407) - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=392407) </details> <!--IssueSummary end--> ### Proposal Now that GitLab.com users can use the GitLab for Slack app for Slack notifications, as part of https://gitlab.com/groups/gitlab-org/-/epics/8670, we want to prevent any *new* Slack Notifications integrations from being created by users of GitLab.com only, but still allow existing Slack Notifications integrations to be edited. ### This issue is blocked by: - People need to be able to configure the GitLab for Slack app at group and instance-level https://gitlab.com/gitlab-org/gitlab/-/issues/391526. - We need to allow people to easily migrate their existing settings from the Slack notifications integration to the GitLab for Slack app integration https://gitlab.com/gitlab-org/gitlab/-/issues/372412. ### Technical implementation These tasks are for ~backend: 1. Hide the Slack Notifications integration from the list of integrations to choose from **for users of GitLab.com only** (`Gitlab.com?`), unless they have one created already. 1. Return an error status code in the API if the [`PUT /projects/:id/integrations/slack` call](https://docs.gitlab.com/ee/api/integrations.html#createedit-slack-integration) were to create the integration **for users of GitLab.com only** (`Gitlab.com?`). (We would allow calls to the endpoint that update existing records).