Fix production deployment

@isaac :

• secrets must not be pushed into the repository
• this includes .env.example file, which is just an example to guide which are the env variables used by the program, this file is just a reference for developers
• use environment variables to populate secret and values that change from production to development environments
• for this file (https://gitlab.igem.org/hq-tech/auth/-/blob/main/src/database/database.ts#L15), use the new environment variables that I created in .gitlab-ci.yml.
• secrets and sensitive values are set by GitLab CI/CD at the project level (not in the repository) https://docs.gitlab.com/ee/ci/variables/#add-a-cicd-variable-to-a-project

Currently, the development deployment does not work: {"status":401,"message":"Client authentication failed: Invalid redirect_uri"}