This really isn’t much different than my old role as Client Services which really boiled down to account management, pre-sales, production management, project management, client relations and “voice of the client” within the company.
You’re just doing this for a development company instead of a digital print company.
In essence, a Community Manager manages a community instead of a client, but it’s really the same job. Maybe a bit harder because at least a company speaks with a single voice and Community Managers are essentially herding cats.
FWIW, it’s impossible to really define Client Services either, as it is not sales and not Customer Care. It’s its own beast.
But at least you know you’re not alone. :-)