groups.rb

desc "V3::Create a group"
      params do
        use :group_params
        requires :send_group_invitation_email,
                 type: Boolean,
                 desc: "Send invitations to group users?"
        optional :private, type: Boolean, default: false
      end
      post do
        group_params = permitted_params.fetch(:group)
        group_params[:organization_id] = current_organization.id
        # sets group_params[:image] or group_params[:regular_image] to proper value
        Activities::Shared.handle_image_change!(group_params)
        created_group = action.call(permitted_params)
        -> tu mi podeślesz to created group 
        group_representer_index.call(created_group)
      end