We are going to release a CICD dCloud lab that has Jenkins/Artifactory/GitLab (not GitHub) integrated. The communication between Jenkins & GitLab will be token-based, as is the communication between the local repo and the remote GitLab repo. I could share the details with you privately if you would like. Does that satisfy your use case or are you thinking of something different?
If you want to directly refer to a private github file from CloudCenter, what you could do is specify a command to download the file, then pipe it to bash. The command to download the file can be found here:
Don't use the -O option though, as that saves the file. Instead so something like
<command to download using token> | bash
All of that would go into the lifecycle action field using the choice "Command or URL"