Fix: Add "Bytes" Field Type support to MongoSchemaCollection

[netizen01]

I'm in the process of migrating my app and ran into a problem. One of my objects has a raw binary data field on it. After migrating my database to mLab, the SCHEMA for this object looks like this:

{
    "_id": "MyObject",
   ...
    "rawData": "bytes"
}

When using the new parse-server package, the server crashes when trying to decode the Binary data in this field. I've traced it down to:

MongoSchemaCollection->mongoFieldToParseSchemaField(type)

This function needs an extra case to handle the "bytes" type when it finds it in the SCHEMA. Here's the complete function that fixes the bug:

function mongoFieldToParseSchemaField(type) {
  if (type[0] === '*') {
    return {
      type: 'Pointer',
      targetClass: type.slice(1)
    };
  }
  if (type.startsWith('relation<')) {
    return {
      type: 'Relation',
      targetClass: type.slice('relation<'.length, type.length - 1)
    };
  }
  switch (type) {
    case 'number':
      return { type: 'Number' };
    case 'string':
      return { type: 'String' };
    case 'boolean':
      return { type: 'Boolean' };
    case 'date':
      return { type: 'Date' };
    case 'map':
    case 'object':
      return { type: 'Object' };
    case 'array':
      return { type: 'Array' };
    case 'geopoint':
      return { type: 'GeoPoint' };
    case 'file':
      return { type: 'File' };
    case 'bytes':
      return { type: 'Bytes' };
  }
}

I tried writing some test cases in the MongoTransform.spec.js but couldn't figure out the correct way of recreating the bug.

[drew-gross]

I've submitted a fix in #1821. The best way to test this would be to add the data directly to mongo through the mongo client, then try to read in the same way you read it in your app. But this is a fairly low risk change I think, so I don't think it needs to be tested heavily. If you want to submit a test, though, we would definitely appreciate it!