Add uniqueness to block email domains (#5692)

app/models/email_domain_block.rb

@@ -4,14 +4,33 @@
 # Table name: email_domain_blocks
 #
 #  id         :bigint           not null, primary key
-#  domain     :string           not null
+#  domain     :string           default(""), not null
 #  created_at :datetime         not null
 #  updated_at :datetime         not null
 #
 
 class EmailDomainBlock < ApplicationRecord
+  before_validation :normalize_domain
+
+  validates :domain, presence: true, uniqueness: true
+
   def self.block?(email)
-    domain = email.gsub(/.+@([^.]+)/, '\1')
+    _, domain = email.split('@', 2)
+
+    return true if domain.nil?
+
+    begin
+      domain = TagManager.instance.normalize_domain(domain)
+    rescue Addressable::URI::InvalidURIError
+      return true
+    end
+
     where(domain: domain).exists?
   end
+
+  private
+
+  def normalize_domain
+    self.domain = TagManager.instance.normalize_domain(domain)
+  end
 end