Expose ot_tracer record?

[garthk]

I can't try on_start_processors and on_end_processors in a unit test to solve #73 without being able to call :opentelemetry.set_default_tracer/1 with a #tracer{}, which I can't consume with Record.extract/2 because it's not in include.

That's not entirely true. I can save the environment, replace it, stop the app, restart it, run my test, stop it again, put back the old environment, and restart it again. You'll feel awful when you review the code, though.

[tsloughter]

You need this accessible in another repo?

When it is just for a test the usual process is to include the header even if it isn't in the include directory.

[garthk]

Yeah, I'll work around it. :/