Implement a way to delete GitHub comments or do a rollback in case anything fails during the creation of a new meeting

Right now, if someone specifies a GitHub issue to reuse when scheduling a new API Review, we add a comment into that GitHub issue before creating the meeting and also before sending the email. We might want to change the order of things so the GitHub comment will be one of the last steps in case something goes wrong.

If something fails when trying to schedule the meeting, we don't have a way to revert that GitHub comment.

For this issue, first we have to think how to refactor the current flows and steps, and get the requiriments for each step (for example, to create a meeting we need to create the GitHub tracking issue first).