Separate API from SDK

[dyladan]

cc: @mayurkale22

Currently a library wishing to integrate OpenTelemetry JS has to import core in order to acquire a tracer from the global tracer registry. core is a part of the SDK and contains many other SDK components.

Proposal: Create a new package named @opentelemetry/api which exposes the public API.

This new package would be the only thing library authors would depend on. It would export all types from the types package, as well as take over the global tracer utils responsibilities from core. Its API surface consists only of the public API and nothing else. This means the functions to get and set the global tracer registry, and types.

[dyladan]

cc: @open-telemetry/javascript-approvers

[mayurkale22]

What if we rename @opentelemetry/types => @opentelemetry/api and move API specific components from core package there?

[dyladan]

I would be fine with that as well

[mayurkale22]

Just wanted to attach original package structure issue: #6. Edit: We considered api name before.

[dyladan]

Just wanted to attach original package structure issue: #6

Thanks. As a separate issue, I want to rename all the packages/opentelemetry-* directories to packages/*. If every package is going to have it then it doesn't seem that important to keep and is annoying to type over and over.