Hi @dda,
Short answer is that the functionality you are describing is not a native feature currently 
The longer answer is that the process can be built using Retool as @bobthebear describes.
There are some options for role mapping and using tools from auth providers for enterprise teams. As well as a plethora of options for setting up a workflow automation that can send over user data to the GitHub API to give the user the necessary permissions.
Is your title say that you are on the Teams plan? Let me know if any of @bobthebear's suggestions would work for your use case and we can help answer more questions about setting that up!