PERF: finalize porting to new incoming links structure

app/models/incoming_referer.rb

@@ -1,4 +1,22 @@
 class IncomingReferer < ActiveRecord::Base
+  belongs_to :incoming_domain
+
+  def self.add!(opts)
+    domain_id = opts[:incoming_domain_id]
+    domain_id ||= opts[:incoming_domain].id
+    path = opts[:path]
+
+    current = find_by(path: path, incoming_domain_id: domain_id)
+    return current if current
+
+    begin
+      current = create!(path: path, incoming_domain_id: domain_id)
+    rescue
+      # duplicates
+    end
+
+    current || find_by(path: path, incoming_domain_id: domain_id)
+  end
 end
 
 # == Schema Information