Add admin API for managing canonical e-mail blocks (#19067)

app/models/canonical_email_block.rb

@@ -5,27 +5,30 @@
 #
 #  id                   :bigint(8)        not null, primary key
 #  canonical_email_hash :string           default(""), not null
-#  reference_account_id :bigint(8)        not null
+#  reference_account_id :bigint(8)
 #  created_at           :datetime         not null
 #  updated_at           :datetime         not null
 #
 
 class CanonicalEmailBlock < ApplicationRecord
   include EmailHelper
+  include Paginable
 
-  belongs_to :reference_account, class_name: 'Account'
+  belongs_to :reference_account, class_name: 'Account', optional: true
 
   validates :canonical_email_hash, presence: true, uniqueness: true
 
+  scope :matching_email, ->(email) { where(canonical_email_hash: email_to_canonical_email_hash(email)) }
+
+  def to_log_human_identifier
+    canonical_email_hash
+  end
+
   def email=(email)
     self.canonical_email_hash = email_to_canonical_email_hash(email)
   end
 
   def self.block?(email)
-    where(canonical_email_hash: email_to_canonical_email_hash(email)).exists?
-  end
-
-  def self.find_blocks(email)
-    where(canonical_email_hash: email_to_canonical_email_hash(email))
+    matching_email(email).exists?
   end
 end