Tech Stack: Docker (Image for Testing)

As a developer, I want to make our GitLab CI job faster by creating a Docker image that contains only the required packages, so we can use for testing jobs.

Note from TA: Issues about Docker Deployment were submitted by two students: @adrika-novrialdi and @__farhanAzmi__. We have splitted this issue into two: Image for Testing (only contains required package), and Image for Deployment. We recommend you to use multi-stage Docker build that will be run in a GitLab CI job. Please discuss about that and determine assignees for those issues.