Migrate Spandex users to Opencensus

[zachdaniel]

Hey all! I'm unsure if this qualifies as an issue here, but it is going to be my first priority on helping standardize observability libraries (for Elixir, at least).

Spandex has a fairly large amount of users, so getting them onto this more standardized and supported solution is important to me and will also bring more production use cases to opencensus libraries. Additionally, Spandex has some ease of use features/an ecto integration, and I will be looking to contribute those to the opencensus ecosystem as well.

Once I'm comfortable that the transition will be easy for Spandex users, I'll be writing a guide on making the jump, and announcing it on all of the repos so that people are aware of what is happening.

[zachdaniel]

@tsloughter Two PRs to opencensus_phoenix that I believe brings it to parity:

opencensus-beam/opencensus_phoenix#4
opencensus-beam/opencensus_phoenix#5

[tsloughter]

Even though we'll have a compatible API it might make sense to wait until we have OpenTelemetry out instead of OpenCensus before sugesting people migrate.

[tsloughter]

I'll get started with opentelemtry-erlang by this weekend and it should go fairly smoothly and mostly be renaming shit from opencensus-erlang.

[hauleth]

@tsloughter maybe in the meantime we should improve some things that I have spotted illogical in OC.