Products like ZenDesk have a whole system built around help centers and tickets.
Discourse and Disqus offer forum-like discussions.
WordPress has several forum plugins.
And that's just what I can think of off the top of my head. My assumption would be that a deeper search on Google will come up with a metric fuckton of options. This is a huge challenge, so I imagine there are tons of companies trying to fill that space.
Hi, I've spent some time thinking through how I would go about implementing a Q&A forum.
I don't think I'd necessarily go the API route. In my company we've implemented Zendesk with a custom URL and theme. It lets us add our unique branding while letting Zendesk handle managing the platform.
You could then leverage Zendesk APIs to bring pieces of the help desk into your application.
I'd be happy to jump on a call with you if you want to explore these ideas more in depth.