Typeorm incompatability with tc39 decorators proposal

typeorm/typeorm#2968

Steps to run this project:

1. yarn install
2. Run yarn start command

tc39 class decorators are supplied not the class constructor, but the descriptor which will be used to create the class.

The export of the module contains the constructed class, so when comparing the export to the annotation capture, they are not ===. This makes EntityMetadataBuilder not find any matching annotated classes.

https://github.com/tc39/proposal-decorators