Family invites (#1397)

* Initial pass at household invites

* Invitee setup

* Clean up add member form

* Lint and other tweaks

* Security cleanup

* Lint

* i18n fixes

* More i18n cleanup

* Show pending invites

* Don't use turbo on the form

* Improved email design

* Basic tests

* Lint

* Update onboardings_controller.rb

* Registration + invite cleanup

* Lint

* Update brakeman.ignore

* Update brakeman.ignore

* Self host invite links

* Test tweaks

* Address missing param error

app/controllers/invitations_controller.rb

@@ -0,0 +1,42 @@
+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