Support for tracing Faraday requests

[solnic]

This adds support for automatic tracing of HTTP requests when using Faraday. It leverages its instrumentation middleware to do the magic.

---

Todo

• Figure out how to use the instrumentation middleware
• Add a Sentry middleware that will set everything up turned out we needed a monkeypatch after all
• Figure out how to enable the integration automatically
• Cover the same cases that are specified by the net/http_spec
• (optional/stretch) unify implementation between net/http MP and faraday extension if we decide to do it, it should go to a separate PR
• Figure out what to do with the default net/http patch

Closes #1795

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.68%. Comparing base (94a8063) to head (c7bfc1d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2345      +/-   ##
==========================================
+ Coverage   98.66%   98.68%   +0.01%     
==========================================
  Files         205      207       +2     
  Lines       13559    13741     +182     
==========================================
+ Hits        13378    13560     +182     
  Misses        181      181              

Components	Coverage Δ
sentry-ruby	99.04% <100.00%> (+0.01%)	⬆️
sentry-rails	97.41% <ø> (ø)
sentry-sidekiq	97.01% <ø> (ø)
sentry-resque	96.79% <ø> (ø)
sentry-delayed_job	98.92% <ø> (ø)
sentry-opentelemetry	100.00% <ø> (ø)

Files	Coverage Δ
sentry-ruby/lib/sentry-ruby.rb	96.66% <100.00%> (+0.01%)	⬆️
sentry-ruby/lib/sentry/faraday.rb	100.00% <100.00%> (ø)
sentry-ruby/spec/sentry/faraday_spec.rb	100.00% <100.00%> (ø)

[sl0thentr0py]

looks great so far!

as you noted in the description, you need to further

• add a breadcrumb
• propagate the tracing headers (sentry-trace and baggage)
  • Distributed Tracing docs here are slightly outdated because we don't add traceparent anymore, I will try to clean those up
• extract relevant request data
  • the span data field keys recorded in DataConventions here are kept in sync with OpenTelemetry Semantic Conventions

[solnic]

@sl0thentr0py http patch is one of the default ones, which means we should skip setting up faraday patch if its adapter is net/http - does this make sense?

[sl0thentr0py]

@solnic yes please!

[sl0thentr0py]

great first PR @solnic!
just a few nits and comments

[sl0thentr0py]

perfect, ty and grats on landing your first PR!

[solnic]

Ahh yes! Thanks for the reviews!