Implement DELETE API for Remote Mirrors

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/355675

Changelog: added
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/82778

doc/api/remote_mirrors.md

@@ -136,3 +136,23 @@ Example response:
     "url": "https://*****:*****@gitlab.com/gitlab-org/security/gitlab.git"
 }
 ```
+
+## Delete a remote mirror
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/82778) in GitLab 14.10.
+
+Delete a remote mirror.
+
+```plaintext
+DELETE /projects/:id/remote_mirrors/:mirror_id
+```
+
+| Attribute   | Type    | Required   | Description       |
+| :---------- | :-----  | :--------- |:------------------|
+| `mirror_id` | Integer | yes        | Remote mirror ID. |
+
+Example request:
+
+```shell
+curl --request DELETE --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/projects/42/remote_mirrors/101486"
+```

lib/api/remote_mirrors.rb

@@ -73,6 +73,29 @@ module API
           render_api_error!(result[:message], result[:http_status])
         end
       end
+
+      desc 'Delete a single remote mirror' do
+        detail 'This feature was introduced in GitLab 14.10'
+      end
+      params do
+        requires :mirror_id, type: String, desc: 'The ID of a remote mirror'
+      end
+      delete ':id/remote_mirrors/:mirror_id' do
+        mirror = user_project.remote_mirrors.find(params[:mirror_id])
+
+        destroy_conditionally!(mirror) do
+          mirror_params = declared_params(include_missing: false).merge(_destroy: 1)
+          mirror_params[:id] = mirror_params.delete(:mirror_id)
+          update_params = { remote_mirrors_attributes: mirror_params }
+
+          # Note: We are using the update service to be consistent with how the controller handles deletion
+          result = ::Projects::UpdateService.new(user_project, current_user, update_params).execute
+
+          if result[:status] != :success
+            render_api_error!(result[:message], 400)
+          end
+        end
+      end
     end
   end
 end

spec/requests/api/remote_mirrors_spec.rb

@@ -99,4 +99,44 @@ RSpec.describe API::RemoteMirrors do
       expect(json_response['keep_divergent_refs']).to eq(true)
     end
   end
+
+  describe 'DELETE /projects/:id/remote_mirrors/:mirror_id' do
+    let(:route) { ->(id) { "/projects/#{project.id}/remote_mirrors/#{id}" } }
+    let(:mirror) { project.remote_mirrors.first }
+
+    it 'requires `admin_remote_mirror` permission' do
+      expect { delete api(route[mirror.id], developer) }.not_to change { project.remote_mirrors.count }
+
+      expect(response).to have_gitlab_http_status(:unauthorized)
+    end
+
+    context 'when the user is a maintainer' do
+      before do
+        project.add_maintainer(user)
+      end
+
+      it 'returns 404 for non existing id' do
+        delete api(route[non_existing_record_id], user)
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+
+      it 'returns bad request if the update service fails' do
+        expect_next_instance_of(Projects::UpdateService) do |service|
+          expect(service).to receive(:execute).and_return(status: :error, message: 'message')
+        end
+
+        expect { delete api(route[mirror.id], user) }.not_to change { project.remote_mirrors.count }
+
+        expect(response).to have_gitlab_http_status(:bad_request)
+        expect(json_response).to eq({ 'message' => 'message' })
+      end
+
+      it 'deletes a remote mirror' do
+        expect { delete api(route[mirror.id], user) }.to change { project.remote_mirrors.count }.from(1).to(0)
+
+        expect(response).to have_gitlab_http_status(:no_content)
+      end
+    end
+  end
 end