Adding configurable e-mail blacklist

app/lib/email_validator.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class EmailValidator < ActiveModel::EachValidator
+  def validate_each(record, attribute, value)
+    return if Rails.configuration.x.email_domains_blacklist.empty?
+
+    record.errors.add(attribute, I18n.t('users.invalid_email')) if blocked_email?(value)
+  end
+
+  private
+
+  def blocked_email?(value)
+    domains = Rails.configuration.x.email_domains_blacklist.gsub('.', '\.')
+    regexp  = Regexp.new("@(.+\\.)?(#{domains})", true)
+
+    value =~ regexp
+  end
+end