stream_handlers customizable

[IciaCarroBarallobre]

Hi,

Would it be possible to make the stream_handlers configurable?

This would make it much easier to integrate OpenTelemetry Cowboy into a project where we are using Kraft.

[eproxus]

Looks good, and thanks for adding an example! Can you make sure the type checkin passes and we can get this merged? ☺️

[IciaCarroBarallobre]

Should we keep extra_src_dirs? When it compiles everything as a single root application, I think it ignores the individual rebar.config files in each example, which means their specific dependencies (like telemetry) aren't loaded into the Dialyzer PLT :(

If we want to keep extra_src_dirs, we could add telemetry to Kraft's main dependencies, but that would broke Kraft's minimalist philosophy by forcing unnecessary dependencies on all users, no? >:(