Document gotchas regarding typekey and fields named "type"

[captaincaius]

Do you want to request a feature or report a bug?

Neither ;) documentation.

What is the current behavior?

I noticed in code that there's special-case code for allowing fields called "type" - detected by type being a POJO with a field that's also called "type"...

1. This special-case workaround isn't documented
2. If we DO document it, we should mention that the workaround only currently works in the case that typeKey is default ("type").

If the current behavior is a bug, please provide the steps to reproduce.

What is the expected behavior?

I think the most logical way would be to mention both points here and reiterate the caveat of point 2 here

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.

master branch

[vkarpov15]

The docs we have are here: https://mongoosejs.com/docs/faq.html#type-key . We'll add notes to the schema type docs