Fix context propagation broken by async@2.x

[bajtos]

Rework the REST middleware to use a hand-written version of "async.eachSeries". Before this change, we were loosing CLS context when the application was relying on the REST middleware to load the context middleware.

This is fixing a problem introduced by post-1.0 versions of async, which we upgraded to via fea3b78.

Related issues

• close LoopBack 2.x branch test failures #3966

Checklist

• New tests added or existing tests modified to cover all changes
• Code conforms with the style
  guide

[hacksparrow]

Why skip? Shouldn't we either make implementation changes to make it pass or remove the test itself with an explanation about its irrelevance?

[bajtos]

Why skip? Shouldn't we either make implementation changes to make it pass or remove the test itself with an explanation about its irrelevance?

You are right, I guess I should not have been lazy. The trouble is that continuous-local-storage is notoriously difficult to get right, but at the same time I don't know if it's ok to remove all CLS/context tests from LB 2.x. I'll give this more thoughts tomorrow.

[bajtos]

@hacksparrow I managed to track down the problem to a difference in behavior of async module between the version 0.9 which was used at the time we wrote the tests, and 1.x/2.x which we use now. I rewrote the relevant part of our code to use our own simplified version of async.eachSeries.

LGTY?

[hacksparrow]

Looks good. 17 checks are failing, though.

[bajtos]

17 checks are failing, though.

Most of them are outside of our control and have been failing for long time.

I checked loopback-getting-started, is has failed on nsp check (unrelated to this pull request). loopback-connector-soap is failing with "Connection fails: Error: connect ETIMEDOUT 139.59.176.153:80" (unrelated). And so on.