Upgrading bootstrap-vue in gitlab-ui

What this post added

This post details how GitLab CI was leveraged to facilitate the upgrade of bootstrap-vue in gitlab-ui. It explains the use of `yarn pack` to create a tarball of an NPM package from a CI job, which is then published as an artifact. This artifact serves as a private registry for development branches, allowing other projects (like GitLab itself) to install and test unreleased versions of the package using `yarn add @gitlab/ui@$DEPENDENCY_URL`. This enabled iterative fixing of breaking changes and collaborative migration. The post also details specific breaking changes in bootstrap-vue 2.0, including import syntax, slot syntax for `BTable` and `BTab`, and refactoring of tooltip/popover components, along with strategies for migrating failing Karma tests to Jest and using `attachToDocument`.