Fixes #29450 - Use sp-references in used taxonomy lookup

Before we relied only on Puppet and Puppet CA proxy features and
searched for hosts which were linked against the proxy in question using
host.puppet_proxy_id and host.puppet_ca_proxy_id fields. When the proxy
didn't have any of these features, the search was unbounded. This meant
we took all the hosts and taxonomy ids from them. This lead to proxy
seemingly being assigned to taxonomies when it really wasn't and not
being able to remove the proxy from such taxonomies.

After this change, we leverage the smart proxy references framework to
really look for hosts reference a given proxy in any way.

app/models/concerns/smart_proxy_host_extensions.rb

@@ -1,14 +1,18 @@
 module SmartProxyHostExtensions
   extend ActiveSupport::Concern
 
+  included do
+    scope :with_smart_proxies, -> { eager_load(ProxyReferenceRegistry.smart_proxy_references.select(&:join?).map(&:join_relation)) }
+  end
+
   module ClassMethods
     # registers a reference to a proxy
     def smart_proxy_reference(hash)
       ProxyReferenceRegistry.add_smart_proxy_reference hash
     end
 
     def smart_proxy_ids(hosts_scope = Host::Managed.all)
-      hosts_scope.eager_load(proxy_join_tables).pluck(proxy_column_list).flatten.uniq.compact
+      hosts_scope.with_smart_proxies.pluck(proxy_column_list).flatten.uniq.compact
     end
 
     # table names containing reference to a proxy

app/models/host/managed.rb

@@ -99,6 +99,7 @@ def build_hooks
   smart_proxy_reference :domain => [:dns_id]
   smart_proxy_reference :realm => [:realm_proxy_id]
   smart_proxy_reference :self => [:puppet_proxy_id, :puppet_ca_proxy_id]
+  smart_proxy_reference :infrastructure_facet => [:smart_proxy_id]
 
   graphql_type '::Types::Host'
 

app/models/smart_proxy.rb

@@ -74,6 +74,13 @@ def ping
     !errors.any?
   end
 
+  def used_taxonomy_ids(type)
+    return [] if new_record? || !respond_to?(:hosts)
+
+    conditions = "#{id} IN (#{Host::Managed.proxy_column_list})"
+    ::Host::Managed.with_smart_proxies.where(conditions).distinct.pluck(type).compact
+  end
+
   def taxonomy_foreign_conditions
     conditions = {}
     if has_feature?('Puppet') && has_feature?('Puppet CA')

test/unit/concerns/smart_proxy_host_extensions_test.rb

@@ -6,6 +6,10 @@ class SmartProxyHostExtensionsTest < ActiveSupport::TestCase
     ProxyReferenceRegistry.references = nil
 
     class ProxyReferrer
+      # SmartProxyHostExtensions is expected to be included into a ActiveRecord model
+      def self.scope(...)
+      end
+
       include SmartProxyHostExtensions
       smart_proxy_reference :test_reference => [:test]
       smart_proxy_reference :test_reference => [:another_test]