Enable users/admins to delete their own/everybody's activities

[dblock]

How do we (or the user) delete a post that Slava bot has made on behalf of a user? There were cases when they wanted to share only some of their public activities on Slack, but not all - and hence they would like to delete some postings by the bot - either by themselves through a command, or though a special management link on a browser, or with the help of a Slava account owner with special privileges.