Hi @berkser
Thanks for your interest in contributing. Welcome to the team 
Hubshare is a stalled project. We may return to development in the near future; however, there are other projects emerging that might eclipse it. Hubshare is pretty limited in scope—it’s basically a publishing service for directories in JupyterHub.
I think all three areas you’re interested in have moved outside the scope of Hubshare.
Define and manage a team of users
This is still an open question, I think, in the Jupyter Hub space. We’ve made some effort at adding an authorization layer to the Jupyter Server. Together with the “groups” API in JupyterHub, we can create a group/role-based access system for managing teams, projects, etc., but it doesn’t currently exist. This should probably be a separate Python API that can be used by JupyterHub Services like Hubshare.
(prometheus?) API for resource monitoring
Depending on what you mean here, Jupyter Telemetry is a new API for enabled structured eventlogging in Jupyter applications. This can be used to track user actions in JupyterHub/Server. If you’re interested in contributing to that effort, we’d love to have you engage in the conversations happening on the jupyter/telemetry repo.
real-time collaboration
This is definitely outside the scope of Hubshare. JupyterLab has been working on a RTC experience (see here). If you’re interested in contributing to that effort, I’d suggest following and engaging in the conversation on that repository. Eventually, I think this would bubble up to the JupyterHub level, which would manage identity+access to a real-time server.
I hope this helps consolidate some ideas for you. There are multiple places we’d love to have you jump in and engage the conversation. Let me know if you have any questions. Thanks!