[AuthenticationMixin] authentication_status to virtual_delegate

Creates a virtual_delegate for AuthenticationMixin#authentication_status
which allows it to be included in reports and put in as part of the main
query.

The biggest thing of note in this change is how the status_severity_arel
is being used to handle the sorting properly in the SQL query.  It makes
use of a SQL's case statement to handle what would normally be a
`sort_by` on the hash lookup of Authentication::STATUS_SEVERITY.
Instead, we match each key to the status column and use that as the
value for the `ORDER BY exp DESC` in the `has_one`, which allows for the
same affect.

This also means that it can inject itself in the `SELECT` of a
`MiqReport`, and avoid N+1's on things like quadicons and such for pages
that use `MiqReport#paged_view_search`.

app/models/authentication.rb

@@ -68,6 +68,26 @@ def self.db_name
     "auth_key_pair_cloud"
   end
 
+  # Builds a case statement that case be used in a sql ORDER BY.
+  #
+  # Generated SQL looks like:
+  #
+  #   CASE
+  #   WHEN LOWER(status) = ''      THEN -1
+  #   WHEN LOWER(status) = 'valid' THEN 0
+  #   ...
+  #   ELSE -1
+  #
+  def self.status_severity_arel
+    arel_case = Arel::Nodes::Case.new
+
+    STATUS_SEVERITY.each do |value, sort_weight|
+      arel_case.when(arel_table[:status].lower.eq(value)).then(sort_weight)
+    end
+
+    arel_case.else(-1)
+  end
+
   def status_severity
     STATUS_SEVERITY[status.to_s.downcase]
   end

app/models/mixins/authentication_mixin.rb

@@ -4,7 +4,16 @@ module AuthenticationMixin
   included do
     has_many :authentications, :as => :resource, :dependent => :destroy, :autosave => true
 
-    virtual_column :authentication_status,  :type => :string
+    has_one  :authentication_status_severity_level,
+             -> { order(Authentication.status_severity_arel.desc) },
+             :as         => :resource,
+             :inverse_of => :resource,
+             :class_name => "Authentication"
+
+    virtual_delegate :authentication_status,
+                     :to        => "authentication_status_severity_level.status",
+                     :default   => "None",
+                     :allow_nil => true
 
     def self.authentication_check_schedule
       zone = MiqServer.my_server.zone
@@ -117,11 +126,6 @@ def missing_credentials?(type = nil)
     !has_credentials?(type)
   end
 
-  def authentication_status
-    ordered_auths = authentication_for_providers.sort_by(&:status_severity)
-    ordered_auths.last.try(:status) || "None"
-  end
-
   def authentication_status_ok?(type = nil)
     authentication_best_fit(type).try(:status) == "Valid"
   end