Shared Template Refactor for a Multi-Service Pipeline

Problem/Feature Description

An engineering team maintains a GitLab CI pipeline for three microservices — auth-service, order-service, and notification-service — all built with the same Node 20 stack. Their current .gitlab-ci.yml has grown to 200+ lines because each service has its own build, lint, and test job with an identical before_script: [npm ci] block and the same image: node:20-alpine line repeated nine times. A new joiner made a change to the setup command last week and only updated four of the nine jobs, causing inconsistent behaviour.

The team wants the pipeline refactored so that the shared setup is defined in one place and inherited by all service jobs. They also want to make sure the pipeline is fast: each service's tests should start as soon as that service's build finishes, not after all three builds complete.

Output Specification

Produce a single .gitlab-ci.yml that covers all three services. Use a reusable template mechanism to avoid repeating the common setup. The file should be noticeably shorter than the 200-line original while preserving the build → test flow per service.