To uninstall ruby-doorkeeper just follow these instructions.
sudo apt-get remove ruby-doorkeeper
This will remove just the ruby-doorkeeper package itself.
sudo apt-get remove --auto-remove ruby-doorkeeper
This will remove the ruby-doorkeeper package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for ruby-doorkeeper then this will work.
sudo apt-get purge ruby-doorkeeper
Or similarly, like this ruby-doorkeeper
sudo apt-get purge --auto-remove ruby-doorkeeper
|Maintainer||Debian Ruby Extras Maintainers <email@example.com>|
|Description||OAuth 2 provider for Rails and Grape|