Added LinkBlock functionality in admin

• Added:
- LinkBlock functionality in admin

app/models/link_block.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+# == Schema Information
+#
+# Table name: link_blocks
+#
+#  id         :bigint(8)        not null, primary key
+#  link       :string           default(""), not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+
+class LinkBlock < ApplicationRecord
+  include LinkNormalizable
+
+  validates :link, presence: true, uniqueness: true
+
+  def self.block?(text)
+    return false if text.nil?
+    return false if text.length < 1
+
+    urls = text.scan(FetchLinkCardService::URL_PATTERN).map { |array| Addressable::URI.parse(array[0]).normalize }
+    url = urls.first
+    link_for_fetch = TagManager.instance.normalize_link(url)
+    where(link: link_for_fetch).exists?
+  end
+end