Add GitHub troubleshooting ops recipe (#242)

content/docs/support-and-ops/ops-recipes/troubleshooting-github.md

@@ -0,0 +1,32 @@
+---
+title: "Troubleshooting GitHub"
+owner:
+- https://github.com/orgs/giantswarm/teams/team-honeybadger
+confidentiality: public
+---
+
+Troubleshooting GitHub related issues.
+
+# Table of Contents
+1. [Deploy key is already in use](#deploy-key-is-already-in-use)
+
+## Deploy key is already in use
+
+Deploy keys are a great way to limit access to a single GitHub repository. The public part of the SSH key is attached
+directly to the repository instead of a personal account. The keys are by default granted only read permission on the
+repository. Optionally they can be granted write access where it can perform the same actions as an organization
+member with admin access.
+
+A deploy key can be attached to a single repository only. Adding it to another one will result in a `Key is already in use` error.
+
+However, you can technically get this error when you added the key to a repository that no longer exists / was deleted
+recently. You probably don't want to reuse the key in such a case but instead generate a new pair and use that.
+
+If for some reason you want to reuse the key and the repository where it was attached is deleted, the reason is that
+GitHub "soft" deletes repositories. It still exists for a time for restoration and the key is still attached to it, it
+is just completely hidden.
+
+1. Organization repositories can be restored under the GitHub organization settings page under `Deleted Repositories`.
+2. Once the repository is restored, remove the key under the `/settings/keys`.
+3. Delete the restored repository again if you don't need it anymore.
+4. Add the key to the new repository.