DEV: Move discourse-affiliate to core (#33749)

https://meta.discourse.org/t/373574

Internal `/t/-/156778`

plugins/discourse-affiliate/plugin.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+# name: discourse-affiliate
+# about: Allows the creation of Amazon affiliate links on your forum.
+# meta_topic_id: 101937
+# version: 0.2
+# authors: Régis Hanol (zogstrip), Sam Saffron
+# url: https://github.com/discourse/discourse/tree/main/plugins/discourse-affiliate
+
+enabled_site_setting :affiliate_enabled
+
+after_initialize do
+  require File.expand_path(File.dirname(__FILE__) + "/lib/affiliate_processor")
+
+  on(:post_process_cooked) do |doc, post|
+    doc.css("a[href]").each { |a| a["href"] = AffiliateProcessor.apply(a["href"]) }
+    true
+  end
+end