Add conditional emission to emits DSL (v0.5.1)

[sebscholl]

Summary

• Adds if: and unless: options to the emits macro for runtime-conditional event emission
• Removes the unused active_model_serializers dependency (was triggering a Rails 8.2 deprecation warning)
• Bumps version to 0.5.1

Conditional emission

Services can now gate whether an event fires based on runtime state — without the event reaching the bus, building a payload, or running validation:

# if: lambda — only emit for large transfers
emits :large_transfer_event, on: :success, if: ->(result) { result.data[:transferred] > 100 }

# unless: lambda — suppress for internal transfers
emits :standard_transfer_event, on: :success, unless: ->(result) { result.data[:internal] }

# if: method reference — only for VIP accounts
emits :vip_transfer_event, on: :success, if: :vip_sender?

# Combine both — both must pass
emits :audit_transfer_event, on: :success,
  if: ->(result) { result.data[:transferred] > 50 },
  unless: :internal_transfer?

Both options accept a lambda/proc or a Symbol naming a private instance method. The condition receives the result object, giving full access to result.data, result.error, result.success?, etc.

Fully backwards compatible — emits declarations without conditions are unaffected.

The with: option is unchanged in behaviour but is now part of **options alongside if: and unless: for a uniform signature.

active_model_serializers removal

The gem was declared as a runtime dependency and required at load time, but nothing in the codebase called into its APIs. Removing it drops one runtime dependency from consuming apps and eliminates the ActiveSupport::Configurable is deprecated warning that AMS was triggering.

Full test suite (768 examples) passes without it.

Changes

File	What changed
lib/servus/events/emitter.rb	emits accepts **options; new emission_condition_met? and evaluate_emission_condition private methods; emit_events_for skips blocked emissions
lib/servus/testing/matchers.rb	Added failure_message_when_negated to emit_event for clean not_to emit_event(...) failures
spec/servus/base_events_spec.rb	13 new tests covering all condition forms and combinations
site/features/event-bus.md	New "Conditional emission" section with examples for all forms
site/testing/services.md	Documents not_to emit_event pattern
lib/servus.rb / servus.gemspec / Gemfile	Removed active_model_serializers
lib/servus/version.rb	Bumped to 0.5.1
CHANGELOG.md	0.5.1 entry

Test plan

• bundle exec rspec — 768 examples, 0 failures
• bundle exec rubocop — no offenses
• No deprecation warnings in test output

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