Midrub allows you to connect the Facebook groups where you are admin. But i don’t recommend you to use this feature if you want to spam a group. Because when you publish from your installation, the owner of the group will see the name and link for your Facebook application. And he can easily report your application and you will lost it.
I didn’t added this feature in Midrub because i want follow and respect the social networks terms and policy. If you want to provide a stable service, you have to follow the terms and policy of each social network.
The autopost’s class for joined groups can be provided on request.