Add and inherit from ApplicationRecord to match Rails 5.0 style

app/models/invite.rb

@@ -1,7 +1,7 @@
 require 'digest/sha1'
 
 # Invites are created by foodcoop users to invite a new user into the foodcoop and their order group.
-class Invite < ActiveRecord::Base
+class Invite < ApplicationRecord
   belongs_to :user
   belongs_to :group
 
@@ -13,9 +13,9 @@ class Invite < ActiveRecord::Base
   validate :email_not_already_registered, :on => :create
 
   before_validation :set_token_and_expires_at
-      
+
  protected
-  
+
   # Before validation, set token and expires_at.
   def set_token_and_expires_at
     self.token = Digest::SHA1.hexdigest(Time.now.to_s + rand(100).to_s)
@@ -32,4 +32,3 @@ class Invite < ActiveRecord::Base
   end
 
 end
-