Cancel workshop feature

[KimberleyCook]

Description of the issue 📄

There are occasions when workshops need to be cancelled. There needs to be a checkbox on the admin page of the workshops that does this. When checked

• RSVP should be closed
• A banner should appear on the workshop page
• All attendees should be emailed
• Workshop reminder email should not be sent

Screenshots 📷

Steps to fix 🛠

To do 📋

• Claim this issue (comment below, or assign yourself if you are part of the codebar org)
• Fork and clone the repository
• Update the relevant files. Follow the steps to fix section in this issue.
• Commit your changes as one commit. Use the title of this issue as your commit message
• Submit a pull request
• Mention this issue in the PR description by including it's number
• Have your pull request reviewed & merged by a codebar team member