Audit change model that is different than entity

This extends `for_changes` method to accept reference of target object
being audited. Previously the `entity` is used to record both scope and
target change object. While that is true in some context (i.e. the
target model happens to be a User/Project/Group), it does not work for
`ApprovalProjectRule` (i.e. the target model is `ApprovalProjectRule`
and the entity is the associated Project)

ee/app/services/ee/audit_event_service.rb

@@ -99,17 +99,19 @@ module EE
 
     # Builds the @details attribute for changes
     #
+    # @param model [Object] the target model being audited
+    #
     # @return [AuditEventService]
-    def for_changes
+    def for_changes(model)
       @details =
         {
           change: @details[:as] || @details[:column],
           from: @details[:from],
           to: @details[:to],
           author_name: @author.name,
-          target_id: @entity.id,
-          target_type: @entity.class.name,
-          target_details: @details[:target_details] || @entity.name
+          target_id: model.id,
+          target_type: model.class.name,
+          target_details: @details[:target_details] || model.name
         }
 
       self

ee/lib/ee/audit/changes.rb

@@ -17,7 +17,7 @@ module EE
       def audit_changes(column, options = {})
         column = options[:column] || column
         # rubocop:disable Gitlab/ModuleWithInstanceVariables
-        @target_model = options[:target_model]
+        @entity = options[:entity]
         @model = options[:model]
         # rubocop:enable Gitlab/ModuleWithInstanceVariables
 
@@ -28,8 +28,8 @@ module EE
 
       protected
 
-      def target_model
-        @target_model || model # rubocop:disable Gitlab/ModuleWithInstanceVariables
+      def entity
+        @entity || model # rubocop:disable Gitlab/ModuleWithInstanceVariables
       end
 
       def model
@@ -67,8 +67,8 @@ module EE
       end
 
       def audit_event(options)
-        ::AuditEventService.new(@current_user, target_model, options) # rubocop:disable Gitlab/ModuleWithInstanceVariables
-          .for_changes.security_event
+        ::AuditEventService.new(@current_user, entity, options) # rubocop:disable Gitlab/ModuleWithInstanceVariables
+          .for_changes(model).security_event
       end
     end
   end

ee/lib/ee/audit/project_feature_changes_auditor.rb

@@ -22,7 +22,7 @@ module EE
 
       def execute
         COLUMNS.each do |column|
-          audit_changes(column, as: column.to_s, target_model: @project, model: model)
+          audit_changes(column, as: column.to_s, entity: @project, model: model)
         end
       end
 

ee/spec/lib/ee/audit/changes_spec.rb

@@ -63,11 +63,11 @@ describe EE::Audit::Changes do
         end
       end
 
-      context 'when target_model is provided' do
+      context 'when entity is provided' do
         let(:project) { Project.new }
-        let(:options) { { model: user, target_model: project } }
+        let(:options) { { model: user, entity: project } }
 
-        it 'instantiates audit event service with the given target_model' do
+        it 'instantiates audit event service with the given entity' do
           user.update!(name: 'Scrooge McDuck')
 
           audit!

ee/spec/services/audit_event_service_spec.rb

@@ -269,6 +269,27 @@ describe AuditEventService do
     end
   end
 
+  describe '#for_changes' do
+    let(:author_name) { 'Administrator' }
+    let(:current_user) { User.new(name: author_name) }
+    let(:changed_model) { ApprovalProjectRule.new(id: 6, name: 'Security') }
+    let(:options) { { as: 'required approvers', from: 3, to: 4 } }
+
+    subject(:service) { described_class.new(current_user, project, options).for_changes(changed_model) }
+
+    it 'sets the details attribute' do
+      expect(service.instance_variable_get(:@details)).to eq(
+        change: 'required approvers',
+        from: 3,
+        to: 4,
+        author_name: author_name,
+        target_id: 6,
+        target_type: 'ApprovalProjectRule',
+        target_details: 'Security'
+      )
+    end
+  end
+
   describe 'license' do
     let(:project) { create(:project) }
     let(:user) { create(:user) }