Slowly getting the nested controllers working

More tests required

app/models/credential.rb

@@ -1,4 +1,5 @@
 class Credential < ApplicationRecord
+    belongs_to :domain
     validates :email, presence: true
     validates :email, uniqueness: true
     validates :email, format: { with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i , message: "email must be valid"}