Auto-stop env kicks off when env is created

**config/feature_flags/development/
  environment_auto_stop_start_on_create.yml**:

Adds a development feature flag for this change.

**doc/ci/yaml/README.md:**

Updates documentation on how auto_stop_in works.

**lib/gitlab/ci/pipeline/seed/environment.rb:**

Updates the seed to set auto_stop_at from auto_stop_in.

**spec/lib/gitlab/ci/pipeline/seed/environment_spec.rb:**

Update spec tests for the environment seed.

config/feature_flags/development/environment_auto_stop_start_on_create.yml

+---
+name: environment_auto_stop_start_on_create
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/47239
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/281449
+milestone: '13.6'
+type: development
+group: group::release
+default_enabled: false

doc/ci/yaml/README.md

@@ -2558,7 +2558,7 @@ In the example above, if the configuration is not identical:
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/20956) in GitLab 12.8.
 
-The `auto_stop_in` keyword is for specifying life period of the environment,
+The `auto_stop_in` keyword is for specifying the lifetime of the environment,
 that when expired, GitLab automatically stops them.
 
 For example,
@@ -2571,8 +2571,8 @@ review_app:
     auto_stop_in: 1 day
 ```
 
-When `review_app` job is executed and a review app is created, a life period of
-the environment is set to `1 day`.
+When the environment for `review_app` is created, the environment's lifetime is set to `1 day`.
+Every time the review app is deployed, that lifetime is also reset to `1 day`.
 
 For more information, see
 [the environments auto-stop documentation](../environments/index.md#environments-auto-stop)

lib/gitlab/ci/pipeline/seed/environment.rb

@@ -12,12 +12,23 @@ module Gitlab
           end
 
           def to_resource
-            job.project.environments
-              .safe_find_or_create_by(name: expanded_environment_name)
+            environments.safe_find_or_create_by(name: expanded_environment_name) do |environment|
+              environment.auto_stop_in = auto_stop_in
+            end
           end
 
           private
 
+          def environments
+            job.project.environments
+          end
+
+          def auto_stop_in
+            if Feature.enabled?(:environment_auto_stop_start_on_create)
+              job.environment_auto_stop_in
+            end
+          end
+
           def expanded_environment_name
             job.expanded_environment_name
           end

spec/lib/gitlab/ci/pipeline/seed/environment_spec.rb

@@ -16,20 +16,37 @@ RSpec.describe Gitlab::Ci::Pipeline::Seed::Environment do
     subject { seed.to_resource }
 
     shared_examples_for 'returning a correct environment' do
+      let(:expected_auto_stop_in_seconds) do
+        if expected_auto_stop_in
+          ChronicDuration.parse(expected_auto_stop_in).seconds
+        end
+      end
+
       it 'returns a persisted environment object' do
-        expect { subject }.to change { Environment.count }.by(1)
+        freeze_time do
+          expect { subject }.to change { Environment.count }.by(1)
 
-        expect(subject).to be_a(Environment)
-        expect(subject).to be_persisted
-        expect(subject.project).to eq(project)
-        expect(subject.name).to eq(expected_environment_name)
+          expect(subject).to be_a(Environment)
+          expect(subject).to be_persisted
+          expect(subject.project).to eq(project)
+          expect(subject.name).to eq(expected_environment_name)
+          expect(subject.auto_stop_in).to eq(expected_auto_stop_in_seconds)
+        end
       end
 
       context 'when environment has already existed' do
-        let!(:environment) { create(:environment, project: project, name: expected_environment_name) }
+        let!(:environment) do
+          create(:environment,
+            project: project,
+            name: expected_environment_name
+          ).tap do |env|
+            env.auto_stop_in = expected_auto_stop_in
+          end
+        end
 
         it 'returns the existing environment object' do
           expect { subject }.not_to change { Environment.count }
+          expect { subject }.not_to change { environment.auto_stop_at }
 
           expect(subject).to be_persisted
           expect(subject).to eq(environment)
@@ -37,9 +54,10 @@ RSpec.describe Gitlab::Ci::Pipeline::Seed::Environment do
       end
     end
 
-    context 'when job has environment attribute' do
+    context 'when job has environment name attribute' do
       let(:environment_name) { 'production' }
       let(:expected_environment_name) { 'production' }
+      let(:expected_auto_stop_in) { nil }
 
       let(:attributes) do
         {
@@ -49,11 +67,41 @@ RSpec.describe Gitlab::Ci::Pipeline::Seed::Environment do
       end
 
       it_behaves_like 'returning a correct environment'
+
+      context 'and job environment also has an auto_stop_in attribute' do
+        let(:environment_auto_stop_in) { '5 minutes' }
+        let(:expected_auto_stop_in) { '5 minutes' }
+
+        let(:attributes) do
+          {
+            environment: environment_name,
+            options: {
+              environment: {
+                name: environment_name,
+                auto_stop_in: environment_auto_stop_in
+              }
+            }
+          }
+        end
+
+        it_behaves_like 'returning a correct environment'
+
+        context 'but the environment auto_stop_in on create flag is disabled' do
+          let(:expected_auto_stop_in) { nil }
+
+          before do
+            stub_feature_flags(environment_auto_stop_start_on_create: false)
+          end
+
+          it_behaves_like 'returning a correct environment'
+        end
+      end
     end
 
     context 'when job starts a review app' do
       let(:environment_name) { 'review/$CI_COMMIT_REF_NAME' }
       let(:expected_environment_name) { "review/#{job.ref}" }
+      let(:expected_auto_stop_in) { nil }
 
       let(:attributes) do
         {
@@ -68,6 +116,7 @@ RSpec.describe Gitlab::Ci::Pipeline::Seed::Environment do
     context 'when job stops a review app' do
       let(:environment_name) { 'review/$CI_COMMIT_REF_NAME' }
       let(:expected_environment_name) { "review/#{job.ref}" }
+      let(:expected_auto_stop_in) { nil }
 
       let(:attributes) do
         {