github custom names recipient not working.

The docs do not include how this should work. The reason for needing custom names is we have multiple GH orgs.

```
subscriptions:
- recipients:
- slack:argocd_actions
triggers:
- on-deployed
- on-health-degraded
- on-sync-failed
- on-sync-running
- on-sync-status-unknown
- on-sync-succeeded
- recipients:
- github.ghdevops
selector: platform=true
triggers:
- on-deployed
- on-sync-failed
- on-sync-running
```

Start by tracing the GitHub recipient configuration represented in the issue and check how the custom name `github.ghdevops` is resolved. Reproduce the shown subscription with multiple GitHub organizations, then confirm that notifications are delivered and the supported configuration is documented.

Written by the indexing model from the issue text.