Add IP-based SMTP authentication (#1149)

db/migrate/20200717083943_add_uuid_to_credentials.rb

@@ -0,0 +1,8 @@
+class AddUUIDToCredentials < ActiveRecord::Migration[5.2]
+  def change
+    add_column :credentials, :uuid, :string
+    Credential.find_each do |c|
+      c.update_column(:uuid, SecureRandom.uuid)
+    end
+  end
+end