Remove introduction for user's who leave

[davis9001]

As a server admin I want to have a command to enable/disable a function of the bot where when it detects that a server member leaves the server any message from the member who left that is in the specified introductions channel is removed.

• There should be a /intro-auto-delete command that can be set to either enable or disable.
• There should be a /intro-channel commannd which specifies the server's introductions channel.
• There should be a /admin-messages-channel command which specifies the private channel where to send message to the admin.
• When a member of the server leaves it should trigger the bot to check for any messages left by that user in the channel set by /admin-messages-channel asking if the admin wants to delete the specified message with an action button to confirm.
• Clicking the confirm button on the admin messages channel message should delete the message in the intro channel.