Add domain search/filter to the "Federation" (/admin/instances) page (#10071)

app/models/domain_block.rb

@@ -24,6 +24,8 @@ class DomainBlock < ApplicationRecord
   has_many :accounts, foreign_key: :domain, primary_key: :domain
   delegate :count, to: :accounts, prefix: true
 
+  scope :matches_domain, ->(value) { where(arel_table[:domain].matches("%#{value}%")) }
+
   def self.blocked?(domain)
     where(domain: domain, severity: :suspend).exists?
   end