Migration to create instance template repository

Templates are important for easily getting started with a project and increase consistency between projects. If a company has a custom license they use for all their projects, it would currently need to be copied into every new project manually.

The first iteration https://gitlab.com/gitlab-org/gitlab-ee/issues/5986 allows a repository to be assigned to this role, but we should enable and configure an instance template repo by default for new and existing instances so that this feature is discoverable and easily accessed.

Proposal

• create a .gitlab group in new and existing instances for user space instance templates including file templates and project templates
• create a _template project containing placeholder file templates (.gitignore, .gitlab-ci.yml, LICENSE, Dockerfile)
• set the instance template repository to this repo

If the group name .gitlab is unavailable (improbable), append a string to the end of the project name to make it unique.

Vendored GitLab templates will not be stored in this repo or group, so that GitLab can easily add/modify/delete templates.

Links / references