Update: Changes to GitLab CI/CD and Docker in Docker with Docker 19.03

This post details a breaking change in the `docker:dind` service introduced in Docker 19.03, which now enforces TLS by default. It provides two solutions for GitLab CI/CD users: configuring GitLab Runner to use TLS by mounting certificates and setting `DOCKER_TLS_CERTDIR`, or disabling TLS by setting `DOCKER_TLS_CERTDIR` to an empty string. It also advises on specifying exact Docker versions to prevent random job failures due to updates.