Allow user to manually specify GitLab personal access token using cli.

[a-t-0]

• [ ] Take it as input argument. (Tokens need to always be different, so instead of asking user, random tokens are selected.)
• [x] If there already is a GitLab pac, overwrite it with new one.
• [x] If it's not yet in personal_creds.txt, append it.
• [x] Pass it to: create_gitlab_personal_access_token to add the token to GitLab docker.
• [x] Create method to safely check if the token works or not.
• [x] Assert the token works.