FEATURE: Restrict link invites to email domain (#15211)

Allow multiple emails to redeem a link invite only if the email domain
name matches the one specified in the link invite.

db/migrate/20211207130646_add_domain_to_invites.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddDomainToInvites < ActiveRecord::Migration[6.1]
+  def change
+    add_column :invites, :domain, :string
+  end
+end