For example, think of something like Firebase.
I don't want something like mongoose, because I don't want to explicitly declare my own models. I want to keep the specifics of the application on the front-end as much as possible, so the server can have minimal configuration.
Is there any node.js library that takes care of this for you? If not, I'm sure lots of people have experience in creating dynamic REST endpoints like this. What insight can you provide?
It doesn't 100% answer what you are asking for, but look at the booster
library I wrote and have been building over the years. http://github.com/deitch/booster
It has automatic generation of endpoints based on the resource you configure. You can set the model fields, validation, post processors, filters, etc. etc. (and associations/relationships are in progress). Look at the README on the github home page for its features and examples.