Explore a simpler/more performed way for context propagation

[raymondfeng]

At the moment, LoopBack uses https://github.com/othiym23/node-continuation-local-storage for implicit context propagation across the async invocation paths. The CLS module has some issues:

1. It adds a lot of overhead
2. Some of the drivers (especially the ones with connection pooling) are not friendly with CLS
   • loopback.getCurrentContext() seems to return null when MySQL is used #878
   • Loopback Context doesn't work with ES connector loopbackio/loopback-connector-elastic-search#15

We should explore a simpler/more performed way for context propagation. One idea is to use the options argument which is now supported for all CRUD operations. strong-remoting can introduce a notation to express the need in remoting metadata to receive the context.

[seriousben]

👍

[ritch]

Here is my proposal: #1495

[bajtos]

Closing in favour of #1495.