Use a method for the has_many :keys in Project

This moves the `where` in the `has_many :keys` association in Project to
the Key model. This allows EE to override this method, instead of
modifying the source code directly.

app/models/key.rb

@@ -34,6 +34,10 @@ class Key < ActiveRecord::Base
   after_destroy :post_destroy_hook
   after_destroy :refresh_user_cache
 
+  def self.regular_keys
+    where(type: ['Key', nil])
+  end
+
   def key=(value)
     write_attribute(:key, value.present? ? Gitlab::SSHPublicKey.sanitize(value) : nil)
 

app/models/user.rb

@@ -88,7 +88,7 @@ class User < ActiveRecord::Base
   has_one :namespace, -> { where(type: nil) }, dependent: :destroy, foreign_key: :owner_id, inverse_of: :owner, autosave: true # rubocop:disable Cop/ActiveRecordDependent
 
   # Profile
-  has_many :keys, -> { where(type: ['Key', nil]) }, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :keys, -> { regular_keys }, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :deploy_keys, -> { where(type: 'DeployKey') }, dependent: :nullify # rubocop:disable Cop/ActiveRecordDependent
   has_many :gpg_keys