fix(error): remove model property from CastError to avoid printing all model properties to console

[vkarpov15]

Fix #14529

Summary

The following script currently prints > 10k lines of output:

'use strict';

const mongoose = require('mongoose');

mongoose.connect('mongodb://127.0.0.1:27017/mongoose_test2');

const TestModel = mongoose.model('Test', mongoose.Schema({ 
  num: { type: Number }
}));

TestModel.findOne({ num: 'foo' }).exec();

Because CastError contains the full model, and Node.js' inspect() seems to ignore custom inspect handlers for error instances. So the above script prints out TestModel and all its subprops, including connections and connection strings in plaintext. This is a bit of a nasty surprise as we saw in #14529.

I did a bunch of digging to try to find some way to get Node's error formatting to avoid printing model, the only approach that seems to work is making model a getter and storing the actual mapping of error -> model in a WeakMap. However that seems a bit excessive.

Examples

[hasezoey]

Looks good to me, just consider maybe putting this in the next minor version instead of a patch

[vkarpov15]

I agree @hasezoey