Summary:
In order to support this the stream inceptor transform nodes now is able to return a list of new meta enties, since these are new attributes we try to mimic what would have happened if they were generated on the client. This makes the rest of the logic downstream simpler
Introduced metadata register, same idea as on the clients.
The attributes available are a mixed bag, will work with blok server to imporove
Reviewed By: antonk52
Differential Revision: D45177781
fbshipit-source-id: 9d761b2f682e7e0fd4710f5b2e9d9d6ff26741fc
7ce19f4359