Migrate from to_hash to to_h

[st0012]

As @solnic pointed out in #2350 (comment) to_hash has special meaning in Ruby and could be called implicitly in contexts like double splatting argument. So we should switch to to_h to avoid potential issues.

Additionally, Matz also explained that in the explicit conversion usages (which is the case for the SDK), to_h should be used.

Compatibility Concern

Since this PR changes the serialization interface of almost all SDK's internal components, if users/libs relied on patching to_hash to extend/modify the data, this could become a breaking change for them. And because to_hash has been that interface since the old sentry-raven SDK (for at least 12 years), I think we can assume at least some legacy apps had built customization on top of it.

For this reason, maybe this should be shipped in 6.0?

(In cases where Configuration#async is set, we use Event#to_json_compatible instead, so they won't be affected)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.63%. Comparing base (7db04c9) to head (0b74d98).

Additional details and impacted files

@@           Coverage Diff            @@
##           6.0-dev    #2351   +/-   ##
========================================
  Coverage    98.63%   98.63%           
========================================
  Files          204      204           
  Lines        13286    13286           
========================================
+ Hits         13104    13105    +1     
+ Misses         182      181    -1     

Components	Coverage Δ
sentry-ruby	99.01% <100.00%> (+0.01%)	⬆️
sentry-rails	97.30% <100.00%> (ø)
sentry-sidekiq	97.01% <100.00%> (ø)
sentry-resque	96.79% <100.00%> (ø)
sentry-delayed_job	98.92% <100.00%> (ø)
sentry-opentelemetry	100.00% <ø> (ø)

Files	Coverage Δ
sentry-delayed_job/spec/sentry/delayed_job_spec.rb	100.00% <100.00%> (ø)
sentry-rails/spec/sentry/rails/activejob_spec.rb	99.42% <100.00%> (ø)
...ry/rails/breadcrumbs/active_support_logger_spec.rb	100.00% <100.00%> (ø)
...readcrumbs/monotonic_active_support_logger_spec.rb	91.54% <100.00%> (ø)
...rails/spec/sentry/rails/controller_methods_spec.rb	100.00% <100.00%> (ø)
sentry-rails/spec/sentry/rails/event_spec.rb	100.00% <100.00%> (ø)
...rails/tracing/action_controller_subscriber_spec.rb	100.00% <100.00%> (ø)
...entry/rails/tracing/action_view_subscriber_spec.rb	100.00% <100.00%> (ø)
...try/rails/tracing/active_record_subscriber_spec.rb	100.00% <100.00%> (ø)
...ry/rails/tracing/active_storage_subscriber_spec.rb	93.02% <100.00%> (ø)
... and 42 more

... and 1 file with indirect coverage changes

[sl0thentr0py]

@st0012 thx! agree that this should be shipped in the next major.

I created a 6.0-dev branch
#2352

can you base this rebase this branch on that branch and change the base there?

[solnic]

Thanks for tackling this! I did not expect you'd address it so quickly ❤️ This is definitely a potentially breaking change, but luckily it's easily fixable in people's codebases.

[st0012]

@sl0thentr0py rebased 👍