Sync versioning with GitLab packaging

Problem to solve

Since AI Gateway is not packaged in the GitLab omnibus/CNG, it's a separate deployment for customers. They need to understand the compatibilities between their GitLab deployment and the additional services. For example, here is the agentk's compatibility assurance. The same issue occurs when they integrate their GitLab deployment with external services example.

However, we're currently releasing AI Gateway on demands. This is hard for customers to understand the compatibilities.

Related to gitlab-org/cloud-connector/gitlab-cloud-connector!3 (comment 2023950251)

Proposal

• Sync versioning with GitLab packages. e.g. GitLab v17.3.x should use AI Gateway v17.3.x.
  • This is basically same with GitLab Runner's compatibility policy.
  • Features may not be available or work properly if a version difference exists.
• We switch to monthly release instead of on-demand release. Automate it via CI or manually do monthly release like Runner's release process.
• Introduce a version file inside AI Gateway. Optionally, introduce a GET version API.
• Document it in AI Gateway repository and https://docs.gitlab.com/ee/administration/self_hosted_models/install_infrastructure.html.
• Make sure changelog are correctly generated for each release in https://gitlab.com/gitlab-org/modelops/applied-ml/code-suggestions/ai-assist/-/releases.

Further details

Links / references