fix: Add Concurrent Ruby dependency to Rails

Rails relies on concurrent ruby for features like async queries.

This results in inconsistent traces since context is not properly propagated between threads.

This change adds Concurrent Ruby as a transitive dependency to mitigate confusion when uses the rails instrumentation independent of the all gem.

Author: arielvalentin

instrumentation/rails/lib/opentelemetry/instrumentation/rails.rb

@@ -21,5 +21,6 @@ module Rails
 require 'opentelemetry-instrumentation-action_mailer'
 require 'opentelemetry-instrumentation-active_record'
 require 'opentelemetry-instrumentation-active_job'
+require 'opentelemetry-instrumentation-concurrent_ruby'
 require_relative 'rails/instrumentation'
 require_relative 'rails/version'

instrumentation/rails/opentelemetry-instrumentation-rails.gemspec

@@ -33,6 +33,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'opentelemetry-instrumentation-active_record', '~> 0.8.0'
   spec.add_dependency 'opentelemetry-instrumentation-active_support', '~> 0.7.0'
   spec.add_dependency 'opentelemetry-instrumentation-base', '~> 0.22.1'
+  spec.add_dependency 'opentelemetry-instrumentation-concurrent_ruby', '~> 0.24.4'
 
   spec.add_development_dependency 'appraisal', '~> 2.5'
   spec.add_development_dependency 'bundler', '~> 2.4'