[server] - improve ``nodeInterface``

[ddanielsantos]

Context

This is how I actually managed to handle nodeInterface, I think that it's the minimum necessary to work.

The problem is that I basically hardcoded the types and if I make any changes to them, I'll need to rewrite that portion of code.

Most of the other people's resolutions to this problem derive from this, here are some examples:

• Bia's koa-server
• Noghartt's fakeddit