Maybe/app/controllers/invitations_controller.rb

class InvitationsController < ApplicationController
  skip_authentication only: :accept
  def new
    @invitation = Invitation.new
  end

  def create
    unless Current.user.admin?
      flash[:alert] = t(".failure")
      redirect_to settings_profile_path
      return
    end

    @invitation = Current.family.invitations.build(invitation_params)
    @invitation.inviter = Current.user

    if @invitation.save
      InvitationMailer.invite_email(@invitation).deliver_later unless self_hosted?
      flash[:notice] = t(".success")
    else
      flash[:alert] = t(".failure")
    end

    redirect_to settings_profile_path
  end

  def accept
    @invitation = Invitation.find_by!(token: params[:id])

    if @invitation.pending?
      redirect_to new_registration_path(invitation: @invitation.token)
    else
      raise ActiveRecord::RecordNotFound
    end
  end

  private

    def invitation_params
      params.require(:invitation).permit(:email, :role)
    end
end