Does anyone know of a good client portal?

I run my own small software development company and I’d like somewhere my clients can login and get access to things like:

• Access to documents from their repo(s) (GitHub, all contracts/etc. are kept here)
• Links to invoices and to pay.
• Milestone progress from their repo(s) (GitHub)
• Links to their test, staging, and production services.
• Ability to get in touch (potentially raising an issue in GitHub).

We’re just doing things manually for now, but before we reinvent the wheel I thought it would be useful to see what’s out there to either use directly or extend.