Fix elasticsearch indexed containers specs

When building these models, a persisted project / namespace is required
because `save!` is called and validation would fail without them

ee/spec/models/elasticsearch_indexed_namespace_spec.rb

@@ -18,8 +18,13 @@ RSpec.describe ElasticsearchIndexedNamespace do
   end
 
   it_behaves_like 'an elasticsearch indexed container' do
+    let_it_be(:namespace) { create(:namespace) }
+
     let(:container) { :elasticsearch_indexed_namespace }
-    let(:attribute) { :namespace_id }
+    let(:container_attributes) { { namespace: namespace } }
+
+    let(:required_attribute) { :namespace_id }
+
     let(:index_action) do
       expect(ElasticNamespaceIndexerWorker).to receive(:perform_async).with(subject.namespace_id, :index)
     end

ee/spec/models/elasticsearch_indexed_project_spec.rb

@@ -8,8 +8,13 @@ RSpec.describe ElasticsearchIndexedProject do
   end
 
   it_behaves_like 'an elasticsearch indexed container' do
+    let_it_be(:project) { create(:project) }
+
     let(:container) { :elasticsearch_indexed_project }
-    let(:attribute) { :project_id }
+    let(:container_attributes) { { project: project } }
+
+    let(:required_attribute) { :project_id }
+
     let(:index_action) do
       expect(Elastic::ProcessBookkeepingService).to receive(:track!).with(subject.project)
     end

ee/spec/models/gitlab_subscription_spec.rb

@@ -254,7 +254,9 @@ RSpec.describe GitlabSubscription do
 
   describe 'callbacks' do
     context 'after_commit :index_namespace' do
-      let(:gitlab_subscription) { build(:gitlab_subscription, plan) }
+      let_it_be(:namespace) { create(:namespace) }
+
+      let(:gitlab_subscription) { build(:gitlab_subscription, plan, namespace: namespace) }
       let(:dev_env_or_com) { true }
       let(:expiration_date) { Date.today + 10 }
       let(:plan) { :bronze }
@@ -271,7 +273,7 @@ RSpec.describe GitlabSubscription do
       end
 
       context 'when it is a trial' do
-        let(:gitlab_subscription) { build(:gitlab_subscription, :active_trial) }
+        let(:gitlab_subscription) { build(:gitlab_subscription, :active_trial, namespace: namespace) }
 
         it 'indexes the namespace' do
           expect(ElasticsearchIndexedNamespace).to receive(:safe_find_or_create_by!).with(namespace_id: gitlab_subscription.namespace_id)

ee/spec/support/shared_examples/models/elasticsearch_indexed_container_shared_examples.rb

@@ -2,15 +2,15 @@
 
 RSpec.shared_examples 'an elasticsearch indexed container' do
   describe 'validations' do
-    subject { create container }
+    subject { create(container, container_attributes) }
 
     it 'validates uniqueness of main attribute' do
-      is_expected.to validate_uniqueness_of(attribute)
+      is_expected.to validate_uniqueness_of(required_attribute)
     end
   end
 
   describe 'callbacks' do
-    subject { build container }
+    subject { build(container, container_attributes) }
 
     describe 'on save' do
       it 'triggers index_project' do
@@ -27,7 +27,7 @@ RSpec.shared_examples 'an elasticsearch indexed container' do
     end
 
     describe 'on destroy' do
-      subject { create container }
+      subject { create(container, container_attributes) }
 
       it 'triggers delete_from_index' do
         is_expected.to receive(:delete_from_index)