Remove changelog_api feature flag

This feature is now ready for use by all our users, so the feature flag
can be removed.

config/feature_flags/development/changelog_api.yml

----
-name: changelog_api
-introduced_by_url: '13.9'
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/300043
-milestone: '13.9'
-type: development
-group: group::source code
-default_enabled: false

doc/api/repositories.md

@@ -281,14 +281,7 @@ Example response:
 
 ## Generate changelog data
 
-> - [Introduced](https://gitlab.com/groups/gitlab-com/gl-infra/-/epics/351) in GitLab 13.9.
-> - It's [deployed behind a feature flag](../user/feature_flags.md), disabled by default.
-> - It's disabled on GitLab.com.
-> - It's not yet recommended for production use.
-> - To use it in GitLab self-managed instances, ask a GitLab administrator to [enable it](#enable-or-disable-generating-changelog-data).
-
-WARNING:
-This feature might not be available to you. Check the **version history** note above for details.
+> [Introduced](https://gitlab.com/groups/gitlab-com/gl-infra/-/epics/351) in GitLab 13.9.
 
 Generate changelog data based on commits in a repository.
 
@@ -562,25 +555,6 @@ In an entry, the following variables are available (here `foo.bar` means that
 - `merge_request.reference`: a reference to the merge request that first
   introduced the change (for example, `gitlab-org/gitlab!50063`).
 
-The `author` and `merge_request` objects might not be present if the data couldn't
-be determined (for example, when a commit was created without a corresponding merge
-request).
-
-### Enable or disable generating changelog data **(CORE ONLY)**
-
-This feature is under development and not ready for production use. It is
-deployed behind a feature flag that is **disabled by default**.
-[GitLab administrators with access to the GitLab Rails console](../administration/feature_flags.md)
-can enable it.
-
-To enable it for a project:
-
-```ruby
-Feature.enable(:changelog_api, Project.find(id_of_the_project))
-```
-
-To disable it for a project:
-
-```ruby
-Feature.disable(:changelog_api, Project.find(id_of_the_project))
-```
+The `author` and `merge_request` objects might not be present if the data
+couldn't be determined. For example, when a commit is created without a
+corresponding merge request, no merge request is displayed.

lib/api/repositories.rb

@@ -211,8 +211,6 @@ module API
           desc: 'The commit message to use when committing the changelog'
       end
       post ':id/repository/changelog' do
-        not_found! unless Feature.enabled?(:changelog_api, user_project)
-
         branch = params[:branch] || user_project.default_branch_or_master
         access = Gitlab::UserAccess.new(current_user, container: user_project)
 

spec/requests/api/repositories_spec.rb

@@ -612,100 +612,83 @@ RSpec.describe API::Repositories do
   end
 
   describe 'POST /projects/:id/repository/changelog' do
-    context 'when the changelog_api feature flag is enabled' do
-      it 'generates the changelog for a version' do
-        spy = instance_spy(Repositories::ChangelogService)
-
-        allow(Repositories::ChangelogService)
-          .to receive(:new)
-          .with(
-            project,
-            user,
-            version: '1.0.0',
-            from: 'foo',
-            to: 'bar',
-            date: DateTime.new(2020, 1, 1),
-            branch: 'kittens',
-            trailer: 'Foo',
-            file: 'FOO.md',
-            message: 'Commit message'
-          )
-          .and_return(spy)
-
-        allow(spy).to receive(:execute)
-
-        post(
-          api("/projects/#{project.id}/repository/changelog", user),
-          params: {
-            version: '1.0.0',
-            from: 'foo',
-            to: 'bar',
-            date: '2020-01-01',
-            branch: 'kittens',
-            trailer: 'Foo',
-            file: 'FOO.md',
-            message: 'Commit message'
-          }
+    it 'generates the changelog for a version' do
+      spy = instance_spy(Repositories::ChangelogService)
+
+      allow(Repositories::ChangelogService)
+        .to receive(:new)
+        .with(
+          project,
+          user,
+          version: '1.0.0',
+          from: 'foo',
+          to: 'bar',
+          date: DateTime.new(2020, 1, 1),
+          branch: 'kittens',
+          trailer: 'Foo',
+          file: 'FOO.md',
+          message: 'Commit message'
         )
-
-        expect(response).to have_gitlab_http_status(:ok)
-      end
-
-      it 'produces an error when generating the changelog fails' do
-        spy = instance_spy(Repositories::ChangelogService)
-
-        allow(Repositories::ChangelogService)
-          .to receive(:new)
-          .with(
-            project,
-            user,
-            version: '1.0.0',
-            from: 'foo',
-            to: 'bar',
-            date: DateTime.new(2020, 1, 1),
-            branch: 'kittens',
-            trailer: 'Foo',
-            file: 'FOO.md',
-            message: 'Commit message'
-          )
-          .and_return(spy)
-
-        allow(spy)
-          .to receive(:execute)
-          .and_raise(Gitlab::Changelog::Error.new('oops'))
-
-        post(
-          api("/projects/#{project.id}/repository/changelog", user),
-          params: {
-            version: '1.0.0',
-            from: 'foo',
-            to: 'bar',
-            date: '2020-01-01',
-            branch: 'kittens',
-            trailer: 'Foo',
-            file: 'FOO.md',
-            message: 'Commit message'
-          }
-        )
-
-        expect(response).to have_gitlab_http_status(:internal_server_error)
-        expect(json_response['message']).to eq('Failed to generate the changelog: oops')
-      end
-    end
-
-    context 'when the changelog_api feature flag is disabled' do
-      before do
-        stub_feature_flags(changelog_api: false)
-      end
-
-      it 'responds with a 404 Not Found' do
-        post(
-          api("/projects/#{project.id}/repository/changelog", user),
-          params: { version: '1.0.0', from: 'foo', to: 'bar' }
+        .and_return(spy)
+
+      allow(spy).to receive(:execute)
+
+      post(
+        api("/projects/#{project.id}/repository/changelog", user),
+        params: {
+          version: '1.0.0',
+          from: 'foo',
+          to: 'bar',
+          date: '2020-01-01',
+          branch: 'kittens',
+          trailer: 'Foo',
+          file: 'FOO.md',
+          message: 'Commit message'
+        }
+      )
+
+      expect(response).to have_gitlab_http_status(:ok)
+    end
+
+    it 'produces an error when generating the changelog fails' do
+      spy = instance_spy(Repositories::ChangelogService)
+
+      allow(Repositories::ChangelogService)
+        .to receive(:new)
+        .with(
+          project,
+          user,
+          version: '1.0.0',
+          from: 'foo',
+          to: 'bar',
+          date: DateTime.new(2020, 1, 1),
+          branch: 'kittens',
+          trailer: 'Foo',
+          file: 'FOO.md',
+          message: 'Commit message'
         )
-
-        expect(response).to have_gitlab_http_status(:not_found)
-      end
+        .and_return(spy)
+
+      allow(spy)
+        .to receive(:execute)
+        .and_raise(Gitlab::Changelog::Error.new('oops'))
+
+      post(
+        api("/projects/#{project.id}/repository/changelog", user),
+        params: {
+          version: '1.0.0',
+          from: 'foo',
+          to: 'bar',
+          date: '2020-01-01',
+          branch: 'kittens',
+          trailer: 'Foo',
+          file: 'FOO.md',
+          message: 'Commit message'
+        }
+      )
+
+      expect(response).to have_gitlab_http_status(:internal_server_error)
+      expect(json_response['message']).to eq('Failed to generate the changelog: oops')
     end
   end
 end