Slash attachments

[Hype3808]

Summary

Add support for slash attachments

Checklist

• [x] If code changes were made then they have been tested.
  • [ ] I have updated the documentation to reflect the changes.
• [ ] This PR fixes an issue.
• [x] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

Confirmations

• [x] I have checked the open PRs and no PR exists like this one.
• [x] My PR focuses on only one issue/change.