Delete a greeting

Delete a greeting by ID
Fix comment

- underscore user_email
- “if users.get_current_user():” instance of “”if
users.get_current_user() is not None:”
Set role
FIx comment

- “is not None” is not necessary
- rename variable for clearly
Fix comment
Merge pull request #11 from nhathv/feature/delete-message

Merged pull request #11, Feature/delete message